Oil stocks and those related to the sector tumbled following the decision by the Organization of the Petroleum Exporting Countries to maintain a steady rate of oil output, which sent the price of Brent tumbling on Thursday.Premier Oil, Enquest, Afren, Hunting, Ophir Energy and Wood Group all took a big hit on Friday afternoon.Premier Oil was also hit by the news its partner Noreco decided to write-off its discoveries in the Huntington field. The oil explorer said it has "never attributed any value to this discovery and its view of the Huntington field reserves has not changed".On the upside, Pennon climbed thanks to an in-line set of results, which reported a 3.8% rise in first-half revenue, but a decline in pre-tax profit.Home Retailer and AO World performed well in line with the wider retail sector as bargain hunters hit the shops looking for a bargain on Black Friday.FTSE 250 - RisersAO World (AO.) 250.60p +7.55%Pennon Group (PNN) 886.00p +4.60%Just Retirement Group (JRG) 137.80p +4.08%Home Retail Group (HOME) 200.10p +2.93%Wetherspoon (J.D.) (JDW) 810.00p +2.92%National Express Group (NEX) 264.90p +2.91%Cineworld Group (CINE) 378.90p +2.38%COLT Group SA (COLT) 136.80p +2.32%Capital & Counties Properties (CAPC) 377.20p +2.14%Galliford Try (GFRD) 1,206.00p +2.12%FTSE 250 - FallersPremier Oil (PMO) 180.00p -16.67%EnQuest (ENQ) 50.25p -13.73%Afren (AFR) 53.10p -8.84%Hunting (HTG) 573.00p -8.54%Rotork (ROR) 2,193.00p -8.20%Ophir Energy (OPHR) 145.00p -8.17%Fenner (FENR) 236.90p -8.14%Wood Group (John) (WG.) 594.00p -7.19%Vedanta Resources (VED) 732.00p -7.11%Elementis (ELM) 257.30p -6.06%