Chevron Corp., Exxon’s biggest US rival, is the only Western oil major to have continued operating in Venezuela while Maduro was in charge. Chevron Vice Chairman Mark Nelson said at the White House meeting on Friday that his company was poised to significantly ramp up output in the country from current levels of about 240,000 barrels per day, and that it could increase production by about 50% over the next 18-24 months.