DOHA: The 2017-18 season of the Qatargas U-23 League will be launched on September 18 with three matchups scheduled at  the opening day.     At Hamad bin Khalifa Stadium, Duhail will take on Al Markhiya before Al Sadd play Qatar Sports Club.     Al Rayyan lock horns with Al Khuraitiyat at Soud bin Abdulrahman Stadium.     A total of 12 teams will feature in the new league that has been devised to prepare the young players for top-flight football in the country.     The 12-team league will be held over 22 weeks with a total of 132 matches scheduled every Monday and Tuesday.     The teams include Al Sadd, Al Rayyan, Duhail, Al Arabi, Al Gharafa, Qatar Sports Club, Umm Salal, Al Khor, Al Siliyah, Al Kharaitiyat, Al Markhiya and Al Ahli.