Abstract: 64 oil and gas reservoirs are divided into three classes according to' their ultimate recovery values. A brief introduction is made for three selected reservoirs Basic equations expressing oil and water flow mechanism are derived, from which the effect of formation dip, sand body rhythm and zonation on the ultimate recovery of waterflooding oil and gas reservoirs is deduced. The discussion of quantitative correlation for the effect of reservoir heterogeneities on the ultimate recovery is emphasized. A multi-variable regression is made between the ultimate recovery and more than 20 parameters from each of the 64 reservoir samples. A correlation is established. which indicates that the waterflooding -controlled oil in place is the major factor affecting the ultimate recovery.