Abstract: Tong's chart method is universally applied in prediction of field waterflooding recovery at home and abroad, but it is only usedin middle-late stage of oilfield development. For high viscosity reservoir with low waterflooding recovery and complex faulted-block oilfield with low permeability, Tong's chart is not used to describe real water cut and recovery percent. This paper presents analyses of some unreasonable problems in Tong's chart method from mathematics and reservoir development theory and improvements of its computing formulae, which widen its applied fields. The case study shows that modified Tong's chart is more reliable and accurate for description of regularity of varied water cut and recovery percent and for prediction of recovery efficiency.

Key words: oilfield development, water injection, water flooding, curve, recovery percent, water cut, chart