The Regularity of Oil and Gas Abundant Accumulation in North Jiangsu Basin, China

摘要

The oil and gas accumulated abundantly in North Jiangsu Cenozoic basin. The basin consists of eleven downwarps seperated by twelve upwarps, but 98% of total proved reserves concentrated on three downwarps-Gaoyou, Jinhu and Qingtong downwarp. These three downwarps have good conditions in petroleum geology: (l)they all were in the position of the area with continuous rapidly depositing during the Cenozoic depocenter moved from west to east;(2)they underwent more intense volcanic activities than other downwarps, so their paleogeothermal gradient was 5-10 'C/kin higher than that of the other downwarps and their threshold depeth of petroleum generation is 400-600 meters shallower than that of other downwnrps. It was controlled by the volcanic activities during the deposition of source rock, Jinhu downwarp deposited high quality source rock with the depth of the oil window from 1200 to 2000 meters, which is 400-800 meters shallower than the other source rocks; (3)they distributed in the good reservoir fncies belts.Fifty oil and gas fields have been explored in the basin, each oil field is small-middle in size, but more than 90% of total proved reserves has been found in fourteen larger oil fields, which distributed in the intersect area of the structural high zones and fault terrace zones of Gaoyou downwarp and Qingtong downwarp, and in the structural high zones of shallow buried marginal facies belts of Jinhu downwarp.