Shushufindi Field, Ecuador's giant, was discovered by Texaco in 1970 and has already produced over 1 billion barrels of oil from Albian- Cenomanian age fluvio-estuarine and marginal marine sands of the Napo Formation. The structure is a 30-kilometer long anticline bounded to the east by a north-south trending reverse fault. When Shushufindi was returned to Petroproduccion after 20 years of development and production, the field was experiencing significant water breakthrough and there was little documented understanding of the reservoirs and the Field's compartmentalization. Now, nearly 30 years after its discovery, a clear model of the field is emerging.