LONDON/HOUSTON, Sept 11 (Reuters) - QatarEnergy is negotiating with several producers to secure multi-year U.S. liquefied natural gas contracts through 2031 to replace capacity knocked out by Iranian attacks that will take years to repair, three trading and industry sources said. Discussions include with Venture Global (VG.N), opens new tab , Cheniere (LNG.N), opens new tab and Woodside (WDS.AX), opens new tab , two of the sources said.