ExxonMobil is expanding its exploration portfolio offshore Greece with a new farm-in agreement for a block in the northwestern Ionian Sea. ExxonMobil, Energean, and Helleniq Energy have reached a farm-in agreement under which the U.S. supermajor will buy 60% in the Block 2 concession in the northwestern Ionian Sea, next to the Italian Exclusive Economic Zone (EEZ), Energean said on Thursday. With Exxon farming-in in the block, Energean’s stake drops to 30%, down from 75%, and Helleniq Energy’s interest in the block falls…