Abstract: Wellblock TZ16-44 is located in the carbonate platform margin in deposition period of Lianglitage formation of Late Ordovician in Tarim basin, which is characterized by such intrafacies as grain bank, reef mound, lime-mud mound and, interbank sea. The reef bank complex composed of different sedimentary microfacies, becomes major depositional types in this area. The study shows that the reefs inside this area distribute in groups or belts along the platform margin, and moderate-low energy psammitic banks are located in the inner side of the reef body. The reefs, the bioclastic banks and the biological psammitic-psephitic banks that are associated in form of upper and lower combination with them are premium reservoir facies, while the moderate-low energy psammitic banks seperately developed in the backreefs are hard to form favorable reservoir facies. So, the bioclastic banks and the biological psammiticpsephitic banks should be important targets for petroleum exploration in this area.

Key words: Tarim basin, Upper Ordovician, reef, deposition, characteristic