Cenozoic tectonic sequence boundary and petroleum geological significance of the Lile Basin, South China Sea

The Lile Basin is a major petroliferous basin with great potential of petroleum resources in the deep-water sea domain of the South China Sea. The key tectonic sequence boundaries S100, S70 and S50 generated during the Cenozoic deposition and filling are discussed in detail in lithology, well logs, palaeontology and seismic reflection profiles in the light of the principles and methods of sedimentology and sequence stratigraphy, and regional tectonic evolution. The tectonic sequence boundaries cited above are considered as the lithologic and electric abrupt surfaces. There are also the saltatory evolution in the biospecies and numbers in the palaeontological evolution at or near the tectonic sequence boundaries. In the seismic reflection profiles, the tectonic sequence boundaries appear as the regional unconformities characteristic of onlap, downlap or truncation. The tectonic sequence boundaries represent the transition of the Lile Basin during the major tectonic evolutionary stages, benefit to the formation of the high-quality reservoir spaces, and serve as the pathways for the long-distance oil and gas migration and the sites of hydrocarbon accumulation in the Lile Basin.