Shell’s big oil spill off Nigeria yesterday reportedly occurred during the transfer of oil to a tanker in their Bonga offshore field.  Oil is produced in the Bonga Field using an FPSO – basically, a modified oil tanker anchored in place.  Oil collected from wells on the seafloor flows up through riser pipes connected to the FPSO.  Shuttle tankers take crude oil out of the FPSO’s storage tanks and carry it to coastal refineries. Here’s a schematic diagram showing the Bonga Field layout:

In March 2011, federal regulators approved the first-time-ever use of FPSOs to develop an offshore field in the US Gulf of Mexico.  Petrobras got the nod for their Cascade-Chinook development in water 8,200′ deep, 160 miles off the Louisiana coast.  Their FPSO, a converted tanker called the BW Pioneer, holds 600,000 barrels of oil (25.2 million gallons). BOEMRE and Coast Guard divvied up oversight responsibility for this vessel / production facility with an MOU in 2009. This project got off to a very poor start when 8,500′ of riser pipe went crashing  to the Gulf seafloor back in early April.

Our main concern is that FPSOs are potentially sources of massive oil spills:  a serious blowout, fire or explosion, collision with another vessel, intentional attack, rogue wave or storm damage, or other incident could result in a near-instantaneous release of millions of gallons. And as we’ve said here before, despite the underwhelming oil cleanup results during last year’s BP / Deepwater Horizon spill, we’ve made no significant progress in our ability to handle big spills.