Yinggehai Sea Basin is situated in the west of Hainan Island and the east of Zhongnan Peninsula and stretches in NW-SE direction.The basin consists of central diapiric zone and a slope zone.Two sets of source rocks including Miocene Yinggehai

Huangliu

Meishan and Sanya Formations and Oligocene Yacheng Formation developed in the diapiric zone.Oil threshold is between 2 800～3 000 m depth.The traps were formed by the upward arch of diapiric fluid

and episodic diapir activity determined hydrocarbon episodic migration.Different migration dynamic forces resulted in different types of oil and gas pools:under high temperature

high pressure and uncompaction

the Miocene source rocks formed high pressure pocket which break overlying strata and formed deep and shallow gas pools;deep seated inorganic CO

2

under high pressure expelled the hydrocarbon gas near fractures

destoried the original gas pools and formed new hydrocarbon gas pools with little Co

2

.