Infill drilling is now recognized as a viable improved recovery process. However, the reliable prediction of incremental recovery by infill drilling cannot be readily and accurately determined by present techniques. This paper proposes a hybrid predictive model of stream tube simulation and numerical simulation by using the contemporary theory of fluid flow in porous media. The model calculates the geometries of stream tubes, remaining oil distribution and water cut at different development stages in the near future, and uses a three-dimensional simulation to track fluid movement in each stream tube slice. This will help reservoir engineers to determine the feasibility of infill drilling. This predictive model is used to forecast the degree of control of well pattern, the ultimate incremental recovery of infill wells within an inverted 5-spot case in an oilfield and the economic benefit is also analyzed.