Analysis of a well that passes through a natural fracture or that has been hydraulically fractured. The fracture is treated as a slab of high permeability that is an effective extension of the actual wellbore. Flow is from the reservoir to the fracture and through the fracture to the well. The pressure-transient analysis for a fractured well can determine the fracture half-length and the fracture conductivity, as well as a fracture-face skin. The skin factor for the fracture is negative and usually ranges from -1. 5 to -5, with an absolute minimum of -6 in rare cases. For effectively infinite-conductivity fractures, the apparent wellbore radius is half the fracture half-length, or x_f/2.