DOHA: Al Duhail sealed their spot in the semi-finals of the Amir Cup with a 2-0 victory over Al Shamal in their quarter-final match at the Suhaim Bin Hamad Stadium on Tuesday.   Kenyan striker Michael Olunga (45+3) and Abdulla al-Ahraq (89) were the scorers for Al Duhail as the defending QNB Stars League champions stayed on for another yet trophy this season.   Five days ago, Sabri Lamouchi's side missed out on a chance to bag their first silverware this campaign after they lost 2-0 to rivals Al Sadd in the final of the Qatar Cup.   Al Shamal defence gallantly stuck to their task. Eventually it took an Olunga strike in first half stoppage time to put Al Duhail ahead before al-Ahraq put the result beyond doubt in the closing stages of the game. Al Duhail will now shift their focus to the Qatar Stars League when they travel away to face Al Kharaitiyat on March 7.   In another quarter-final match on Tuesday, Al Rayyan edged out Al Kharaitiyat 2-0, thanks to a brace by Ivorian Yohann Boli, who struck once in each half.