A seal assembly for a nested dual drill pipe includes a tube having a female seal assembly and a male seal assembly at the longitudinal ends. The female seal assembly includes a larger internal diameter portion, a taper adjacent thereto and a smaller internal diameter portion adjacent to the taper. The male seal assembly includes a smaller external diameter portion, a seal groove adjacent thereto and a larger external diameter portion adjacent to the seal groove. The smaller internal diameter portion and the larger external diameter portion have diameters selected to enable free longitudinal movement of the male seal assembly into the female seal assembly while limiting axial displacement to maintain the seal ring fully energized.