By Arathy Somasekhar HOUSTON, June 12 (Reuters) - Exxon Mobil was poised to name Alex Volkov as head of global trading, two sources with knowledge of the matter said. On Thursday, Reuters reported that sources said Tracey Gunnlaugsson, who led the trading division since 2023, was set to retire. Exxon declined to comment. Reuters could not immediately reach Volkov for comment. Volkov, based in Texas, has spent nearly three decades at Exxon, holdi…