oa Field-scale Heterogeneity of Carbonate Reservoirs from the Arab Fm – Lessons Learned from Seven Case Studies

Preparation of robust reservoir model from the Arab Fm relies on thorough characterization of the different carbonate facies from core and thin section examination. However the key step remains to properly extrapolate the detailed facies recognition in cored wells to uncored wells. The objective of this presentation is to illustrate how electrofacies have been successfully first calibrated on few cored wells and then extrapolated to all uncored wells in several hydrocarbon fields in UAE (5 fields) and Qatar (2 fields). The sedimentary interpretation of the Arab reservoirs from the different studied fields is primarily based on the integration of: - high-resolution stratigraphic architecture of the carbonate-evaporite series allowing subdivision of the reservoir interval into meter-scale stratigraphic units, - recognition of depositional and diagenetic trends within each stratigraphic unit in order to constrain the distribution of the main facies. Special attention was paid to properly define along selected cored wells a number of pre-rock types; each of them being characterised by a specific log signature and porosity/permeability relationship. Once this calibration exercise has been carried out, the pre-rock types have been propagated to uncored wells. The robustness of the propagation needs to be validated by few blind tests on cored wells not used in the calibration step. This method has proved to be successful in recognition of the main reservoir facies including grain-supported facies affected by tar mat deposition. Preparation of maps per stratigraphic units where both thickness and proportion of electrofacies are displayed on well basis is used to constrain the field-scale distribution of reservoir facies taken into account the depositional and diagenetic trends provided by regional paleogeographical reconstruction. Results from the seven field case studies will be highlighted during the presentation.