Oil prices rose Friday on expectations that cold weather could boost demand for petroleum products. For the week, however, prices posted losses as ample global supplies continued to weigh on the market. Brent, the global benchmark, posted a seventh weekly loss, while the U.S. benchmark fell for a sixth straight week. Oil prices have slid for months, hitting multiyear lows Tuesday, on concerns that the Organization of the Petroleum Exporting Countries is unlikely to cut its output to reduce a global glut of oil.