丽水凹陷晚古新世海平面变化及有利储层分布预测

据 9口钻井的岩性、古生物、重矿物及测井等资料 ,结合地震资料 ,对丽水凹陷晚古新世海平面变化进行了分析 ,并对有利储层的分布进行了预测。晚古新世丽水凹陷经历了两次较大规模的海侵。第一次海侵发生在灵峰组沉积晚期 ,规模相对较小 ,位于凹陷中部的灵峰凸起构造带仍出露水面 ,成为局部物源区 ;此时期在凹陷边缘主要形成扇三角洲沉积体系 ,在凹陷中心区形成浅海沉积体系并伴有重力流沉积。第二次海侵发生在明月峰组沉积中期 ,规模比第一次大 ,不仅使凹陷边缘成为浅海环境 ,而且灵峰凸起构造带也沉没于水下 ,变为碳酸盐岩台地和浅海环境 ;在这次海平面升降过程中 ,凹陷陡坡带发生多次重力滑塌 ,于凹陷深水区形成多期次的浊积扇体 ,在区域上这些浊积扇体位于丽水西次凹的沉降和沉积中心区。丽水凹陷已发现的含油气储层主要是位于两次海侵最大海泛面之下的深水浊积扇砂体 ,类似的砂岩储层在丽水西次凹分布还较广泛 ,但以紧邻灵峰凸起构造带西侧凹陷中心区的明月峰组最为有利

LATE PALEOCENE SEA-LEVEL FLUCTUATIONS AND PREDICTION OF FAVOURABLE RESERVOIRS IN LISHUI SAG,EAST CHINA SEA BASIN

According to the data of lithology, palaeontology, heavy minerals, logging and seismic in 9 wells, the Late Paleocene sea_level fluctuations are analysed and the favorable reservoirs are predicted in Lishui sag. During Late Paleocene there were two greater transgressions in the sag. The first one occurred in Late Lingfeng, during which Lingfeng salient belt in the central Lishui sag was still not inundated and became a local provenance. In the meantime, there were fan delta systems along the margin of the sag, and neritic deposition systems with gravity flow in the central sag. The second transgression, greater than the first, may occur in Middle Mingyuefeng, during which the sag margin was shallow sea and Lingfeng salient was inundated and became a carbonate platform. Meanwhile, multiple gravity slumps took place on the steep slope of the sag, turbidity fans formed in its deepwater area that is the center of subsidence and deposition in the western sub_sag. In Lishui sag, the discovered oil_gas bearing reservoirs are mainly deepwater turbidity fan sandstones under the maximal flooding surfaces of the two transgressions. But similar sandstones developed more widely in the western sub_sag, of which the best ones are in Mingyuefeng Formation in the central sag adjacent to the west side of Lingfeng salient belt.