An improved method for continued drilling operation s with a single one-piece wellhead for drilling multi-wellbores eliminating the step of blowout preventer removal after drilling a second wellbore. An operator utilizing the improved method may utilize a single one-piece wellhead while drilling a series of wellbores through the blowout preventer with differing diameters without removing and reinstalling the blowout preventer between each drilling operation, eliminating testing of the seals after the reinstallation of the blowout preventer between the drilling subsequent wellbores.