We present a simple quantum perturbative full dimensionality model to study field emission from a graphene blade within the frame of the Bardeen transfer Hamiltonian formalism. The material electronic wavefunction is obtained for a multidimensional square well potential specifically designed to reproduce 2 important characteristics of the material, the Fermi level and the shape of the emitting orbitals. The wavefunction in the vacuum between the electrodes is obtained with a close coupling method in a finite domain. Our model provides the emitted current density with respect to the applied field. This allows to discriminate the different functional forms proposed to fit the Fowler-Nordheim emission curves. Our model also provides information on emission patterns. Electron total energy distributions are computed for different field intensities and compared with other theoretical and experimental results.