U.S. crude stockpiles are climbing at their quickest pace since 2016, fueling fresh volatility in the oil market as fears of excess supply gather momentum. Rising inventories have powered a 11% drop in oil since prices hit a nearly six-month high in late April, with analysts wary that increased production from the Organization of the Petroleum Exporting Countries and its allies could cause another glut. Those worries have oil teetering around closely watched levels below which further declines could hurt energy companies and…