Shell (NYSE:RDS-A) (NYSE:RDS-B) can confirm it has a loss of 319 barrels of drilling fluid from a booster line on one of its contracted drilling rigs in the Gulf of Mexico.
A booster line provides additional drilling fluids and is separate from the wellbore itself. The leak was isolated and stopped. Remedial action has been approved by the regulator (BSEE), and this includes temporarily abandoning the Appomattox well, pulling the drilling riser, and making appropriate repairs.
The drilling fluid is synthetic, biodegradable, and is described in the Material Safety Data Sheet (linked below) from M-I L.L.C. (A Smith/Schlumberger Company), a contractor for Shell. The Appomattox field is located in the Mississippi Canyon area of the Gulf of Mexico.
Once there were indications of a leak, a source was identified, and at no time was there safety or well control issues. The integrity of this well was also not compromised.