Fracture density evaluation using well logs and oil production data in an onshore oil field

Conventional well logs cannot detect fractures in hydrocarbon reservoirs. Drilling core data are costly and this puts a significant limitation on data acquisition. The image logs, with their specific technology and by implementing electrical and sonic characteristics of the formation, can recognise various features in the borehole wall, including bedding, fracture, sedimentary structures, faults, condition of fractures, whether mineral-filled, etc. This investigation uses image logs (FMI, OBMI, and UBI) of five wells in different Iranian oil fields. The studied area is located in the central part of the northern Dezful embayment. The fracture values in each zone of the Asmari Formation of studied wells were calculated, and each zone's fracture density histogram was drawn. The maximum and the minimum number of fractures were recognised, and reservoir zones with a high production potential were defined. Mud loss and cumulative oil production data were converted to histograms and compared with fracture density histograms. The results showed that there was a good correlation between the three histograms. Based on these research results, well log image diagrams can determine the exact location and calculate the fractures density to determine the appropriate reservoir zones.