This study defines and investigates the Hydraulic Interwell Connectivity (HIC) concept to characterize and estimate the reservoir connectivity. This approach is an integrated study of reservoir characterization, geostatistics, production performance and reservoir engineering. In this study HIC is quantitatively defined as the ratio of observed fluid flow rate to a maximum possible (ideal) flow rate between any combination of any two wells in the producing unit. The spatial distribution of HIC was determined for the net pay of a reservoir by geostatistics. It was used as a guide for selecting infill well locations to optimize waterflood infill drilling. A low permeability carbonate reservoir producing unit, J.L. Johnson