Oil prices have been slip, sliding away since midyear. Reuters

Crude-oil futures moved marginally higher Friday, but finished lower for the week, with key exporting nations refusing to cut output amid a supply glut and forecasts for weak crude demand the world over. The Intercontinental Exchange Brent December contract gained 57 cents, or 0.7 percent, to close at $86.10 per barrel Friday. The benchmark price lost 4.9 percent for the week as a whole.

The ICE WTI November contract edged higher to close at $82.85 per barrel Friday. However, the light, sweet crude lost 3.6 percent for the week.

Members of the Organization of the Petroleum Exporting Countries, or OPEC -- the group of 12 mostly Middle Eastern producers that pump about one-third of the world’s oil -- are scheduled to meet in November in Vienna, and traders will track their decisions on production targets.

Producers such as Saudi Arabia, Kuwait and the United Arab Emirates plan to oppose any cut in the OPEC oil-production ceiling at the meeting, the Wall Street Journal reported.

Goldman Sachs Group Inc. said in a note to clients that crude oil’s selloff has been fueled by investor positioning based on expectations rather than a real-world disparity between supply and demand, and that if prices dropped low enough, they could trigger renewed demand and consumption, Bloomberg News reported. The investment bank said “prices have likely overshot to the downside.”

Oil prices dropped by more than $1 per barrel Thursday, when Brent crude hit a fresh four-year low at less than $83, amid growing concerns over the health of the global economy.

The International Energy Agency, or IEA, this week cut its oil demand growth forecast for 2015 as global economies remain weak, prompting predictions that OPEC members might prefer selling at lower prices over losing their markets.