关键词: 海湾, 海相, 烃源岩, 盆地, 河流

Abstract:

About 80% of discovered oil reserves in the world is sourced from marine source rocks (about 20% from lacustrine facies), and the main control factors of oil reservoir are diversified in different oil-bearing basins. As viewed from global basins, the most important and most common accumulation control factor is oil source, i.e., "source control" is the most important. The major global marine basins are studied through exploring the formation conditions of marine source rocks, and it is discovered that the Persian Gulf Basin, the West Siberia Basin, the Mexico Gulf Basin, the North Sea Basin, the Atlantic Ocean Basin, the East Africa coast Basin, Sichuan Basin, Tarim Basin and Paleo-Tethys Ocean and other basins were all gulfs during the formation period of chief source rocks, i.e., the lands existed in three sides, and a majority of gulfs had only one water channel (a minority had 2-3 water channels) connected to the ocean. The gulf is the most favorable estuary for river. After passing the weathering denuded zone, the river dissolves a large number of minerals to bring the elements including phosphorus, iron and potassium to the gulf as the main nutrients for aquatic organisms such as algae (the nutrients brought by oceanic upwelling is unable to reach the gulf). Because of the seawater replacement between gulf and ocean with blocked communication, the high concentration of nutrient is maintained, and thus can guarantee the long-term reproduction of aquatic organisms such as algae. The small winds and waves in gulfs are favorable to the organic matter preservation, so as to form high-quality source rocks. The relationship between the organisms and rivers in modern oceans and lakes, such as the Bohai Sea, East Sea, South China Sea, Taihu Lake and Dianchi Lake, are studied to further confirm that the main nutrients for aquatic organisms growing are derived from the rivers on land.

Key words: gulf, marine, source rock, basin, river