SUMMARY

Like other South East Asian areas, the north-west margin of the East Vietnam Sea (South China Sea) is characterized by petroleum reservoirs not only restricted to Tertiary sediments, but also in the Pre-Cenozoic basement rocks. The consolidation of basement of the Cenozoic basins was formed by the closure of the Tethys Ocean that lead to continental convergence and formation of foreland basins in the Late-Mesozoic. The Cenozoic basins are characterized by graben and depression structures caused by Oligocene passive rifting and Miocene sagging. Oligocene sediments in the central grabens are composed of lacustrine clastics and olistostromes in places. Some of these are good reservoir targets; other parts consist of lacustrine shales, which provide both source rocks and effective cap-rocks. Miocene sediments are widely distributed throughout all Cenozoic basins on the north-west margin of the East Vietnam Sea, such as the Beibu Wan, Song Hong, Quang Da, Phu Khanh, and South Hainan basins. The Miocene sediments of Beibu Wan, Song Hong basins are represented by deltaic clastics; but in Quang Da, Phu Khanh and South Hainan basins, marine clastic and carbonate successions predominate, occasionally with carbonate reefs. The association of Oligocene-Miocene source rocks and seals with reservoirs both on fractured carbonate basement highs and in Oligocene-Miocene clastics and reef-carbonates, is common feature throughout the study area.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah