The analytic study of the monophasic steady state flow towards a horizontal well gives the expression of its productivity and a description of the pressure field. A local criterion is derived out of it for the comparison of drainage efficiency between horizontal and vertical wells as well as a global criterion usable at the whole reservoir scale. The water cresting effect, induced by the hydrocarbons production with a horizontal well in presence of a second liquid phase is exactly described in two dimensions with an analytic solution. Permeability anisotropy and several feed mechanisms are coped with. In order to allow comparisons, a water coning model below a vertical well taking permeability anisotropy into account is established.