松辽盆地梨树断陷深部层系沉积特征及演化分析

Sedimentary features and evolution of deep series in Lishu Fault Depression, Songliao Basin

  • 摘要: 通过对松辽盆地梨树断陷大量钻井岩心、测井资料及地震相的综合研究,对梨树断陷的沉积相特征及其演化研究表明,梨树断陷形成初期,基底被一组同生断裂切割,发育多个小型断陷,随着沙河子组沉积早期湖平面的上升,逐渐形成由桑树台断裂控制的箕状断陷,“西断东超、北超”的构造格局控制着统一水体的广盆沉积。具有深湖—半深湖相、滨浅湖、扇三角洲、三角洲及水下扇、浊积扇为主的沉积组合特征。断陷盆地的沉积演化经历了从裂陷初期的浅水湖盆—沼泽到半深湖—深湖,再到半深湖—浅湖,最后为滨浅湖—河流—三角洲的充填过程。据梨树断陷油气勘探开发成果及沉积相分析,梨树断陷深层有利的含油气储层在断陷时期各个层段均有发育,主要以扇三角洲前缘及三角洲前缘水下分流河道、河口坝微相和重力流水道砂体为主,有利储层主要分布于断陷北部杨大城子地区、东部斜坡的双龙—大榆树—小城子地区。

     

    Abstract: According to the drilling cores, well logging and seismic facies data of the Lishu Fault Depression, the analyses of sedimentary features and evolution showed that the basement was cut by syngenetic fractures and seve-ral small fault depressions developed during the early stage. As lake plane rose during the early Shahezi period, a half-graben fault depression controlled by the Sangshutai Fault developed gradually. A structural pattern featured by fault in the west and overlap in the east and north controlled wide basin deposition in an unified water system. The sedimentary assemblage was characterized by deep/semi-deep lake, shallow lake, fan delta, delta, submerged fan and turbidite fan. The fault depression developed from shallow lake basin-swamp, to semi-deep/deep lake, and to semi-deep/shallow lake, and finally to shallow lake-river-delta. The exploration and sedimentary facies analyses of the Lishu Fault Depression showed that favorable reservoirs generated in every formation during fault depression evolution, mainly as fan delta front and delta front underwater distributary channel, mouth bar microfacies and gravity channel sand body. The Yangdachengzi area in the north and the Shuanglong-Dayushu-Xiaochengzi area in the east were favorable for exploration.

     

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