Natural gas futures tumbled to the lowest in almost three years as U.S. shale output swamps the market amid mild spring weather, soothing concern about a potential supply crunch next winter. A seasonal lull in heating and cooling demand, coupled with surging production, is accelerating gains in stockpiles of the fuel in underground caverns and aquifers. While inventories are more than 30 percent below normal, they’re poised to refill quickly: Analysts predict that stored supplies probably rose by more than quadruple the average last week. Though gas demand has climbed as new U.S. export terminals send super-chilled cargoes to buyers as far away as Japan, soaring production continues to dog the market. In the Permian Basin of West Texas and New Mexico, where the fuel is pumped as a byproduct of oil exploration, gas supply has […]