A mobile well drilling apparatus for a drilling site with clustered wells includes a substructure. A mast includes hinging points and fixing points. The mast is hinged to the substructure via the hinging points, about which the mast rotates between a horizontal and a vertical position. A drill floor includes a first portion hinged to the mast, and a second portion fixed to the mast and moving integrally therewith; and a draw-works permanently installed on the substructure. The substructure includes first and second sub-bases. The sub-bases are parallel and spaced apart. The first portion of the drill floor includes a connection portion facing one of the sub-bases. The hinging points are connected to one of the sub-bases. In operation, the fixing points are connected to the opposite sub-base. Each sub-base includes hydraulic walking devices adapted to move the well drilling apparatus between the clustered wells on the drilling site.