This paper focused on the sedimentary characteristics of shallow stratum in the Yihezhuang area of Yellow River Delta and its impact on choosing the seismic excitation layer.Global climate was transformed from Last Glacial Maximum to post glacial since the late stage of Late Pleistocene.Affected by sea level eustacy and channel migration of Yellow River,the sedimentary characters in the Yihezhuang area of Yellow River delta which located in continental-marine interaction zones was complicated.A comprehensive analysis of the sedimentary characteristics in this area were performed from the aspects of stratigraphic division and contrast,the characteristics of sediments and sedimentary evolution.The study showed that this area formed a continental-marine interaction stratum pattern affected by the paleogeographic condition.The stratum was divided into 5 units from bottom to top,including the Upper Pleistocene and Kenli Formation,the 1st Member of the Wuhaozhuang Formation,the 2nd Member,the 3rd Member,and the Diaokou Formation.The results also indicated that the sedimentary evolution experienced 5 stages:from the late stage of Late Pleistocene to the early stage of Early Holocene,the late stage of Early Holocene,the Middle Holocene,the early stage of Late Holocene,and the late stage of Late Holocene,respectively.Correspondingly,fluvio-lacustrine facies,tidal flat facies,neritic facies,tidal flat facies and delta facies were developed.Furthermore,this research provided effective guidance for the exploration and production in oil field.The selecting principle in oil-gas exploration of seismic excitation layer in Yihezhuang area was proposed by analyzing comprehensively the formation lithology,depth,ghost reflector and low velocity layer.The depth from 16 to 18 meters was confirmed the best excitation layer,and seismic data obtained from this layer had wider frequency band,higher frequency and more abundant low-frequency information.%晚更新世晚期以来全球气候由末次冰期冰盛期向冰后期转化,受海平面升降和黄河河道迁移的影响,地处海陆交互地带的黄河三角洲义和庄地区沉积特征复杂.利用14个浅层钻孔、沉积物粒度、微体古生物、孢粉、重矿物、14C测年等资料,从地层划分与对比、沉积物特征、沉积演化等方面对该区晚更新世晚期以来的沉积特征进行了综合分析.研究表明,受古地理条件影响,研究区形成海陆交替的地层格局,地层自下而上划分5个单元,即上更新统+垦利组、五号桩组一段、二段、三段及钓口组;沉积演化相应经历5个阶段,包括晚更新世晚期至早全新世早期、早全新世晚期、中全新世、晚全新世早期和晚全新世后期,依次发育河湖相—潮坪相—浅海相—潮坪相—三角洲相.在沉积特征研究的基础上,综合分析地层岩性、深度、虚反射面和低速带等因素,提出了该区油气勘探中地震激发层的选取原则,并据此确定五号桩组一段的潮坪沉积(16～ 18 m深度)是最佳激发层位,有效指导油田勘探工作.
展开▼
