Examine the "insertion tube" that is BP's latest and most desperate intervention* at its gushing "riser" pipe on the gulf sea floor. Its floppy daisy-wheel flange isn't made to form a seal and BP doesn't say it will. It's to plug the riser "as much as possible," they say--except that plugging the pipe is not their priority. If stopping the ongoing contamination were their foremost goal, would their approach be to try to cram a second tube in beside the flanged one, and to inject a stream of anticoagulant--methanol--to keep oil flowing up the insertion tube?
The priority seems to be to collect oil for sale--which is so much easier to do from a well than from a slick or from seawater. There's lots of appliances for plugging pipes, and what BP's using isn't one of them.
* Actually, the very latest is that the insertion tube failed, so that at last BP will try to stopper their gushing well.