Tectonic Controlling Factors of Ordovician Reef and Bank Reservoir in Tazhong Uplift in Tarim Basin

The analysis of structure and reservoir along Tazhong No.1 belt in the northern Tazhong uplift of Tarim basin shows that in the Ordovician reef and bank without reconstruction there only exists low-porosity and low-permeability reservoir,and the tectonic action controls the development of high-productivity reservoirs.In the end of the reef and bank deposition of the Lianglitage formation in Tazhong No.1 zone,intensive exposed karstification with large caverns was formed due to the uplift of the eastern structure,the reservoir quality in the eastern area is better than that in the western one.The faulted belts are the main locations where large fractures and caverns with anomaly beaded seismic response developed.The fracture-cavern bodies formed by dissolution in multistage burials are mainly controlled by the faults.So,the fractures have constructive effects on post dissolution and reservoir permeability,also,it is significant factor for high oil-gas production.The structural differentiation in Tazhong No.1 zone allows the distribution of reef and bank body and the development of reservoirs to be of subsection property.The eastern platform margin is in high,steep,long and narrow location,in which the fracture-cavern reservoirs well developed due to weathering crust karstification and structural action,being favorable for high and stable petroleum production.The western area with underdeveloped faults has broad but ramp platform margin dominated by low porous reservoirs.