SINGAPORE-* Qatar Petroleum has cut the number of spot al-Shaheen crude cargoes it offered for September loading by half to two, down from four cargoes in August, trade sources said on Thursday

* The drop in supply was likely due to a scheduled field maintenance at the oilfield, they said

* QP offered two 500,00-barrel cargoes to load on Sept. 21-22 and 28-29 in a tender which will close on July 16, with bids remaining valid for a day

* Traders estimated that there will be about 12 cargoes to be exported in September versus 16 in August

(Reporting by Florence Tan; Editing by Rashmi Aich) ((Florence.Tan@thomsonreuters.com; +65 6870 3497; Reuters Messaging: florence.tan.thomsonreuters.com@reuters.net))