LONDON—Recent shifts in the relative price of different crude grades have dealt oil exporters from the vast Atlantic Ocean basin the best chance in months to sell to top consuming region Asia, but sales have been sluggish as COVID-19 fears cool demand. The Omicron coronavirus variant has curbed oil consumption in Asia just as U.S. and West African sellers pinned their hopes on the changing market structure paving an easier path eastward than competing oil from the Middle East. Global benchmarks Brent and West Texas Intermediate crude were pummelled last week as tight supplies eased with U.S. strategic petroleum reserve (SPR) sales and a decision by the Organization of Petroleum Exporting Countries and their allies to boost output. Brent crude’s premium to Dubai quotes sank to $2.56 a barrel last week, the lowest since March, making the export of Atlantic Basin crude oil grades more attractive for Asian buyers, according …