Chevron has quietly cut the price of Venezuelan crude sold to U.S. refiners after American forces seized a tanker off the country’s coast, tightening an already-fragile export channel and adding fresh volatility to Gulf Coast markets. Traders familiar with the matter told Bloomberg that Chevron sold a batch of Venezuelan crude on December 11 at weaker levels than a similar offer just two days earlier. The timing was impossible to miss: the discount came immediately after U.S. forces boarded and seized the Skipper, a sanctioned crude carrier…