Bilinear flow occurs in horizontal wells draining fractured reservoirs because of the transient dual-porosity behavior originating during the intermediate linear-flow period. Bilinear flow is identified by analyzing the transient-pressure response at the point where the pressure derivative exhibits the characteristic one-quarter slope on the log-log diagnostic plot. However, the duration of the transient dual-porosity behavior depends on system geometry, namely location and length of the horizontal well and thickness of the producing layer, and on the permeability contrast, which reportedly exists between the more conductive fractures and the feeding matrix.