Spill, baby, spill.

First, saw the end of the pipe to make it flush. Make a jig to fit over the pipe. On top of the jig, a threading tap is mounted inside a bearing which allows the tap to turn. The bearing is attached to vertical supports that have grooves down which the bearing, and the tap, can slide. The robot arm will operate the tap to make internal threads in the pipe. The flutes in the tap will allow sufficient oil to escape to enable the tapping operation to take place against the preassure. A steel cap to fit over the pipe will be already welded onto the shank of the tap so that the tap can be used as the plug, instead of removing the tap, then screwing in a plug. I don't know if this would work. Perhaps someone can tell me why it wouldn't.