The United States oil company Chevron has taken full responsibility for a leak off the coast of Brazil which leaked hundreds of barrels of oil per day into the sea.
A subsidiary company says the leak from the undersea well has been plugged.
Frade chief executive George Buck told a news conference that they underestimated the pressure in the offshore oil reservoir and overestimated the strength of undersea rock.
The well is now being abandoned. It was drilled by Transocean from the Sedco 706 rig.
The leak occurred about 160km off the coast of Rio de Janeiro state.
At its peak, the ANP regularly agency said about 200 - 330 barrels per day were leaking through cracks in the seafloor.
Chevron owns 52% of Frade. Another 30% is owned by Petrobras of Brazil. A Japanese Group known as Frade Japan owns 18%.
Petrobras was last year awarded a permit to explore the Raukumara Basin off the east coast of New Zealand for gas and oil.