not shown with its associated flow control valves may be provided over the blow out preventer 126 the flow control valves associated with the lubricator control the discharge of the returning drilling fluid from the lubricator the subsea wellbore 90 is drilled by a drill bit carried by a drill string which includes a drilling assembly or a bottom hole assembly u201c bha u201d 130 at the bottom of a suitable tubing such as continuous tubing 142 it is contemplated that jointed tubing may also be used in the invention the continuous tubing 142 is spooled on a reel 180 placed at the vessel 101 to drill the wellbore 90 the bha 130 is conveyed from the vessel 101 to the wellhead equipment 125 and then inserted into the wellbore 90 the tubing 142 is moved from the reel 180 to the wellhead equipment 125 and then moved into and out of the wellbore 90 by a suitable tubing injection system fig1 shows one embodiment of a tubing injection system comprising a first or supply injector 182 for feeding a span or loop 144 of tubing to the second or main tubing injector 190 a third or subsea injector not shown may be used at the wellhead to facilitate injection of the tubing 142 in the wellbore 90 installation procedures to move the bottom hole assembly 130.