Fatih Birol, Executive Director of International Energy Agency (IEA), speaks at a press conference in Houston, Texas, the United States, on March 11, 2019. The second wave of U.S. shale revolution is coming and it will shake up the international oil and gas trade flow, Fatih Birol said at the press conference. The 38th CERAWeek kicked off Monday in Houston, the fourth largest city in the United States. (Xinhua/Liu Liwei)