The preliminary agreement by Russia, Saudi Arabia, Venezuela and Qatar to freeze output has already put a floor under crude prices and a deal this weekend to include other producers would extend the recovery, according to Qatar’s Energy Ministry. Analysts and traders have puzzled over exactly why oil producers have devoted so much diplomatic energy to the meeting in Doha on April 17, when the consensus is that the freeze would have little immediate impact on crude production. The letter — an invitation to the Doha meeting that Norway declined — gives some answers. Qatar, which is hosting talks between at least 15 countries to finalize the accord, told Norway’s Ministry of Petroleum and Energy that the plan to cap output at January levels has already “changed the sentiment of the oil market,” according to a letter from Energy Minister Mohammed Al Sada obtained by Bloomberg through a freedom-of-information […]