1 atm =33ft 14.7 psi, Pneumatic pressure at surface would need to be 2,227 Air PSI, not including Friction loss for material. Basically, you would be unable to keep H2O from creeping back up the straw... Nice thinking outside the box though.
So your saying take MOPN Canon 5000 feet under water and shoot the sorbent towards the leaking well head? does MOPN Canon function under water? I don't understan what your saying.