In this contribution we analyze numerically the optical properties of the graphene wire medium, which unit cell consists of a stripe of graphene embedded into dielectric. We propose a simple method for retrieval of the isofrequency contour and effective permittivity tensor. As an example of the graphene wire medium application we demonstrate a reconfigurable hyperlens for the terahertz subwavelength imaging capable of resolving two sources with separation λ0/5 in the far-field.