Reef complexes are ideal oil and gas reservoirs because of their high porosities. The key elements in the analysis of reef complex reservoirs include the identification of sequence units, analysis of hydrocarbon history of source rocks, and characterization of porosities. The development of reef complex reservoirs is controlled by sea-level changes, sedimentary paleogeography, diagenesis, and tectonic evolution of the basins. The huge oil reservoirs in the Upper Ordovician Lianglitag Formation in the Tazhong Uplift are prime examples of reef complex reservoirs. A case study of the Well Shun 6 shows that the Lianglitag reservoirs were formed during deep burial and characterized by multiple periods of hydrocarbon filling. Multiple tectonic events resulted in the concentration of oil and gas in the slope-break belt.