Falling oil prices could push half of U.S. tight-oil production out of the market, OPEC’s secretary-general said Wednesday, suggesting the group expects an end to a global oil glut that has driven oil prices down by 25% to about $85 a barrel in recent months.

Speaking at the Oil and Money conference in London, Abdalla Salem el-Badri, OPEC’s secretary-general, said, “At this [current] price, 50% of tight oil will be out of the market.”