THE DEEPWATER OIL AND GAS EXPLORATION PROSPECT IN THE NORTHERN CONTINENTAL MARGIN OF SOUTH CHINA SEA

Deepwater oil and gas exploration and production are steadily increasing in these years. CNOOC has signed ten deepwater contracts with foreign companies by the end of 2006, after 12 virgin deepwater blocks in the South China Sea (SCS) were invited to partner for the oil and gas exploration and development work in 2002. The proven source rocks are the early Oligocene mid-deep lacustrine mudstone, transitional mudstone, marine mudstone and coal system. The probable source rock is the Eocene mid-deep lacustrine mudstone, and the possible one is the upper Oligocene and Miocene marine mudstone. There are at least three reservoir cases in deepwater, including Oligocene transitional sandstones, Neogene-Quaternary marine deepwater sandstone and reef, and Eocene terrestrial sandstone. The seal rocks are developed widely, and the Neocene marine mudstone is the regional seal. There are a lot of traps with the main styles of draping anticline, fault trap and deepwater fan. The deepwater play and traps contain bulge, secondary bulge in sag, fault zone and deepwater fan. Exploration activity should first aim at the structural traps in the sag and in the forward direction of structure around the sag and then gradually develop toward the non-structural t rap. The discovery of natural gas reserves exceeding 100 billion cubic meters in a prospect well named LW3-1-1, located at the Pearl River Mouth Basin, shows a favorable petroleum conditions in the northern continental margin of SCS.