Reservoir characterization methods are very important as they provide a better description of the storage and flow capacities of a hydrocarbon reservoir; moreover it plays crucial role in reservoir simulation models. Carbonate reservoirs show challenges to engineers and geologists to characterize because of their tendency to be tight and generally heterogeneous due to depositional and diagenetic processes. Among the various quantitative rock-typing techniques presented in the literature, the hydraulic flow unit method (RQI/FZI) is more widely used. 'D' is a main carbonate formation for one of the giant gas reservoir in Iran. In this study, available routine core data from four wells are assembled to develop improved generalized permeability porosity relationship for characterize 'D' formation by (HFU) concept.For this purpose, three wells are considered to develop HFU transforms for 'D' formation. Correlation accuracy of each discrete rock type (DRT) was very good (R2>0.9) for horizontal permeability. Then all data from different wells were combined to determine generalized porosity permeability relationship for 'D' formation. This transform was tested for its accuracy on available core data of fourth well which exist in the same formation. Calculated permeability data by HFU technique matched very well with the routine core data which confirm the accuracy of generalized HFU transform. In the same manner, generalized vertical permeability relationship was developed for 'D' formation and tested for its accuracy

The concern over fossil energy shortage for the next decade leads to the extensive research activities in the area of enhanced oil recovery. Steam injection as one of well known EOR process has been used for about five decades to improve the oil production rate and recovery efficiency. Steam flooding is applied to heavy and extra-heavy oil reservoirs; however it could be used in light oil reservoirs in which water injection do not work effectively. Regardless of different performances, this method is an efficient EOR process for both heavy and light oil reservoirs. In this work, two separate numerical models were prepared to investigate steam flooding performance for the recovery of light and heavy oil. The heavy oil model is a Cartesian hypothesis model with properties of Cold Lake heavy oil reservoir in Canada and light oil model is a sector of an Iranian fractured light oil reservoir. For this purpose, steam flooding was implemented in these two models separately. Then according to software options, all possible recovery mechanisms (viscosity reduction, steam distillation, thermal oil expansion and others) were simulated individually to measure the effectiveness of each recovery mechanism in total recovery of heavy and light oil during steam flooding. Also, operational parameters such as steam quality, steam flow rate and well perforation were optimized for both reservoirs. Results show that steam flooding performances in heavy and light oil reservoirs are different. Heavy oil reservoirs do not response fast to steam compared to the light oil reservoirs. Furthermore, viscosity reduction is a main recovery mechanism in recovery of heavy oil and contribute to 80% of total recovery, while in recovery of light oil all three main recovery mechanisms have the same contribution to total recovery. It was also found that the optimized operational parameters are different for each reservoir.

Steam flooding is applied to heavy and extra-heavy oil reservoirs, but it may be used in light oil reservoirs when water injection does not work effectively. In this simulation study, the feasibility of the steam flooding method applied as enhanced oil recovery process to one Iranian oil-wet fractured reservoir is investigated. For this purpose, a simulation model based on a sector of this reservoir was prepared and history matched with available production data. Steam flooding has been simulated for this reservoir and has been compared with conventional water injection process. A sensitivity analysis has been performed in order to study the effects of important parameters. The results show that the steam flooding process is likely to be profitable for this reservoir, when compared with water injection, improving the oil recovery factor by nearly 14 %.