西湖凹陷杭州斜坡带的烃源岩特征与勘探方向

Geochemical Characteristics and Exploration Direction of Hydrocarbon Source Rocks in Hangzhou Slope Zone of Xihu Sag

位于东海盆地西湖凹陷西北部的杭州斜坡带目前的勘探程度还较低。依据现有探井钻遇地层的有关分析数据,分析了杭州斜坡带烃源岩的品质、沉积环境、母质来源、沉积相特征。在杭州斜坡带钻遇的平湖组烃源岩级别为差等,宝石组烃源岩为差—中等。平湖组和宝石组烃源岩均发育于弱还原的沉积环境,母质主要以浮游动植物和混合来源为主。平湖组地层表现出近源、粗粒、厚砂的辫状河三角洲沉积特征。宝石组地层表现出辫状河三角洲前缘—局限海沉积特征,向东在沉积相带上比平湖组更早出现局限海泥岩。下一步的勘探方向应向东扩展,向距离烃源中心更近、储盖组合更优越的地方转移。

At present,the exploration degree of the Hangzhou slope belt,which is located in the northwest of Xihu sag,East China Sea basin,is relatively low.The quality,sedimentary environment,parent material source and sedimentary facies of the source rocks in the Hangzhou slope belt are analyzed according to the relevant analysis data of strata encountered in exploration wells.The source rocks in Pinghu formation encountered in the slope of Hangzhou are of poor grade,and the source rocks in Baoshi formation are of poor-medium grade.The source rocks of Pinghu formation and Baoshi formation were developed in weakly reductive sedimentary environment.The parent material is mainly phytoplankton and mixed source.The Pinghu formation is characterized by braided river delta deposition with near-source,coarse grain and thick sand.The formation of Baoshi formation shows the characteristics of braided river delta frontal-restricted Marine sediments.To the East,the limited marine mudstones appeare earlier in the sedimentary facies belt than in Pinghu formation.The exploration direction of the next step should be extended eastward to the place closer to the center of source rocks and better reservoir and cap combination.