Using a reservoir simulator, a reservoir model state is obtained. The reservoir model state is used to trace streamlines to obtain streamline trajectories and detect fluid fronts along the streamlines. Using the streamline trajectories, the streamlines are connected to wells. The streamlines are grouped for multiple granularity levels, into groups to obtain a grouping hierarchy. Through the granularity levels of the grouping hierarchy, fluid front time of flights are determined for the groups, and target flowrates assigned to completion devices based on the fluid front time of flights to obtain target flow rates. A completion design is presented that incorporates the target flowrates.