PERMIAN LITHOFACIES PALEOGEOGRAPHY OF THE SOUTH YELLOW SEA AREA, LOWER YANGTZE PLATE AND ITS IMPLICATIONS FOR PETROLEUM EXPLORATION

Taking the series as the mapping unit, the Permian lithofacies paleogeographic map series for the South Yellow Sea have been compiled based on the comprehensive studies of outcrops and drilling, logging and seismic data. Upon the basis, the distribution of favorable Permian source rocks and reservoirs are analyzed for revealing the petroleum potential and exploration directions. The results of the study suggests that the Lower Yangtze area was a tectonically stable passive continental margin in Permian time. Topographically, it was low in the middle along a NE-SW axis and high on northwest and southeast flanks. There developed various types of sedimentary facies, such as deltaic facies, coastal-marsh facies, restricted platform facies, open platform facies, slope facies and basin facies. According to the correlation between source rocks and lithofacies paleogeography, it is inferred that the coal measures of the Longtan Formation, which are widely distributed in the Lower Yangtze area from southeast Anhui to southeast Jiangsu, and the offshore area of central part of the South Yellow Sea Basin , are the main source rocks, and the east and southeast of the Central Uplift are the most favorable exploration targets since they are quite close to the hydrocarbon generation center, where occur well-developed deltaic reservoirs, superior oil and gas migration pathways and excellent preservation conditions.