ABSTRACT The Safaniya reservoir is the main producing reservoir in the Safaniya Field, the largest offshore oil field in the world. It lies within the Wasia Formation of Middle Cretaceous Albian age, and was deposited in a fluvial dominated deltaic environment. The southern part of the field is dominantly thick, massive sands, while the northern part is more heterogeneous, with all types of sub-deltaic environments; distributary channels, mouth bars, crevasse splays and interdistributary bay shales, prodelta shales, and shallow marine shales and sands. The complex heterogeneity of the reservoir provides a challenge in characterizing reservoir behavior. To better understand fluid movement; lateral water encroachment, and water fingering in the reservoir architecture context, a 3-D electrofacies model (Abbott, 1982) was constructed for the Safaniya reservoir. It is based upon a detailed 11-layer geologic description, used an electrofacies database of 573 of the 624 total wells in the field, and was built using a 3-D geocellular modeling program. The model has an area of 3900 sq. km. The modeled vertical interval from top Mauddud to Base Dair marker averages 540 feet in thickness. Cell dimensions of the model are 250m X 250m areally and 1 foot vertically. Reservoir thickness is several hundred feet which yields a total 3-D model of 45.5 million cells. This electrofacies model is available to generate various maps and cross sections to help in reservoir management decision making and to provide 3-D geologic input for multi-layer reservoir simulation models.