钱塘江口地区冰后期沉积特征与生物气聚集

钱塘江口冰后期底界面是末次冰期低海面时形成的区域不整合面。冰后期沉积可划分为初、早、中、晚4期,对应接受4期沉积。初期为河床砂砾沉积,早期为河漫滩粘土和砂质粘土沉积,中期为淤泥质粘土沉积,晚期为粉砂、湖沼粘土和粉粘土沉积。沉积相主要有河床相、河漫滩相、浅海相、河口湾相、湖沼相、滨海相和陆相坡积洪积风化红土等7种类型,它们的分布与古河谷的形成演化和海平面的变化密切相关。河漫滩相和浅海相砂质透镜体为超浅层生物气最有利和较有利的储集带。

SEDIMENTARY CHARACTERS AND BIOGAS ACCUMULATION IN POSTGLACIAL STRATA OF QIANTANGJIANG RIVER MOUTH REGION

The bottom boundary of the postglacial strata in Qiantangjiang River Mouth region is recognized as the surface of the regional unconformity formed during the lower sea level period of the last glacial age.The postglacial strata can be divided into four sets corresponding to primary,early,mid and late stages.Channel grails deposited in the primary stage,alluvial flat clay rock and sandy clay rock deposited in the early stage,mudstone deposited in the mide stage,silty clay and limnic clay deposited in the late stage.Sedimentary facies include river bed,alluvial flat,neritic,river mouth and limnetic,littoral,weathered continental drift bed and flood deposit facies.It is suggested that the sandy lenticular bodies of alluvial flat and neritic facies are favourable reservoir zones for ultra shallow biogas exploration.