Qatar Petroleum, the world’s largest producer of liquefied natural gas, said Tuesday it plans to increase natural-gas output by 30% over the next seven years, as the small emirate faces a diplomatic crisis with its Persian Gulf neighbors. Qatar Petroleum will double the size of a major project in a massive subsea Persian Gulf gas field shared with Iran, Chief Executive Saad al-Kaabi said in a news conference in Doha on Tuesday. The expansion will bring Qatar’s total LNG production to 100 million tons a year—the…