Goldman Sachs says the world has more oil than it had thought and expects prices to slip below $40 per barrel, and maybe lower, because the glut may linger deep into next year.

On the same day, the International Energy Agency said production outside OPEC countries will drop sharply in 2016 with prices so weak.

Goldman analyst Damien Courvalin said these cuts may not be enough. He lowered his forecast for 2016 to $45 per barrel from $57. He said prices could collapse to around $20 if production decreases too slowly.

Oil markets have been unusually volatile, with the price of crude down 26 percent in three months.