摘要
为精确划分松辽盆地沙河子组层序地层,限定断陷期沙河子组与营城组地层时代,进而研究断陷期盆地的演化,笔者利用松辽盆地大陆科学钻探松科2井获取的下白垩统地层岩芯资料,从岩芯尺度对沙河子组与营城组界面进行揭示,结合过松科2井地震剖面解释、松科2井及邻井测井响应特征分析和岩芯精细描述,总结出沙河子组顶界面在不同尺度的具体特征:(1)在地震剖面尺度,其表现为明显上超的特征;(2)在测井曲线上,界面附近表现为由下到上自然伽马曲线变化幅度增大,双侧向电阻率曲线由低值变为中高值的特征;(3)岩芯尺度上,表现为细粒沉积的砂泥岩突变为砾岩或火山岩。
To accurately divide the sequence stratigraphy of Shahezi Formation,restrict the stratigraphic age of Shahezi Formation and Yingcheng Formation in rifting stage and study the basin evolution during the period of fault depression,complete core data of the Lower Cretaceous from the continental scientific drilling borehole in Songliao Basin( SK2) is used to identify the boundary between Shahezi Formation and Yingcheng Formation. Combined with the interpretation of seismic profile across SK2,the analysis of logging response characteristics of SK2 and adjacent wells as well as detailed core description,the specific characteristics of the top boundary of Shahezi Formation at different scales are summarized in this study.(1) On the seismic profile scale,the boundary is associ-ated with obviously onlap.(2) On the well log,the amplitude of variation of natural gamma-ray logging curve has increased from the bottom to the top near the boundary,and the dual laterolog curves change from low to medium-high value,respectively.(3) On the core scale,the boundary is underlain by fine grained sandstone and mudstone,and overlain by conglomerate or volcanic rock.