福山凹陷下第三系流沙港组沉积体系及演化特征
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摘要
运用地质、测井、地震及岩芯等综合方法 ,对福山凹陷下第三系流沙港组的沉积体系进行了研究。流沙港组主要发育辫状河三角洲相和湖泊相两种沉积体系。根据沉积环境和沉积物特征 ,将辫状河三角洲沉积相划分为辫状河三角洲平原亚相、辫状河三角洲前缘亚相和前辫状河三角洲亚相。其中以三角洲前缘亚相为沉积主体 ,其内沉积构造丰富 ,侧积交错层理发育。湖泊相沉积体系也可划分为 4个亚相 ,即浅湖亚相、半深湖亚相、深湖亚相及湖底扇亚相。其中湖底扇亚相比较发育 ,特点是扇相砂体、砂砾岩体与深水泥岩页岩间互出现 ,垂向上表现为推进式复合叠置、向上变厚变粗的层序。流沙港组自盆地中心至盆地边缘的沉积模式为湖底扇—深湖—半深湖—三角洲前缘—三角洲平原。沉积物源主要来自福山凹陷的南部。流沙港组二段发育一大套黑色泥岩 ,为主要生油岩层和盖层 ,流沙港组三段和一段南部的辫状河三角洲前缘亚相带为储集性能较好的厚层砂体 ,从而使该组构成了良好的生储盖配置关系 ,因此流沙港组是福山凹陷值得进一步勘探的有利层位。
Through composite method of geological, log, seismic and core analyses, depositional system of Eogene Liushagang Fm in Fushan sag has been studied. Braided delta and lacustrine facies are two major depositional systems developed in Liushagang Fm. The braided delta facies can be divided into three sub-facies: delta plain sub-facies, delta front sub-facies and pro-delta sub-facies based on depositional environment and sedimental features. Among which,the delta front sub-facies constitutes the main body of sediments characterized by abundant sedimentary structures, such as the lateral-accretionary cross beddings. The lacustrine depositional system can also be divided into four sub-facies, i.e. shallow lacustrine, moderate lacustrine,deep lacustrine and sublacustrine fan sub-facies.The sublacustrine fan deposit is relatively well developed and characterized by the interbeddings of sand bodies,glutinites, and mudstone and shales.It is vertically characterized by progading and composite stacking,and thickening and coursening upward sequences. The lateral evolution of Liushagang Fm shows the evolutional patterns of sediments from basin center to basin margin to be sublacustrine fan,deep lacustrine, moderate lacustrine,delta front,and delta plain.The sediments have mainly sourced from the southern part of Fushan sag. Very thick black mudstone occurring in the 2nd member of Liushagang Fm constitutes the main oil source rock and caprock;while the thick sandbodies in braided delta front sub-facie belt, developed in the 1st member and 3rd member of Liushagang Fm,would be good reservoirs,both of them would constitute a good combination of source,reservoir and cap rocks.The Liushagang Fm in Fushan sag would,therefore,be the target of further exploration.
Through composite method of geological, log, seismic and core analyses, depositional system of Eogene Liushagang Fm in Fushan sag has been studied. Braided delta and lacustrine facies are two major depositional systems developed in Liushagang Fm. The braided delta facies can be divided into three sub-facies: delta plain sub-facies, delta front sub-facies and pro-delta sub-facies based on depositional environment and sedimental features. Among which,the delta front sub-facies constitutes the main body of sediments characterized by abundant sedimentary structures, such as the lateral-accretionary cross beddings. The lacustrine depositional system can also be divided into four sub-facies, i.e. shallow lacustrine, moderate lacustrine,deep lacustrine and sublacustrine fan sub-facies.The sublacustrine fan deposit is relatively well developed and characterized by the interbeddings of sand bodies,glutinites, and mudstone and shales.It is vertically characterized by progading and composite stacking,and thickening and coursening upward sequences. The lateral evolution of Liushagang Fm shows the evolutional patterns of sediments from basin center to basin margin to be sublacustrine fan,deep lacustrine, moderate lacustrine,delta front,and delta plain.The sediments have mainly sourced from the southern part of Fushan sag. Very thick black mudstone occurring in the 2nd member of Liushagang Fm constitutes the main oil source rock and caprock;while the thick sandbodies in braided delta front sub-facie belt, developed in the 1st member and 3rd member of Liushagang Fm,would be good reservoirs,both of them would constitute a good combination of source,reservoir and cap rocks.The Liushagang Fm in Fushan sag would,therefore,be the target of further exploration.
引文
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3 纪友亮.陆相断陷湖盆层序地层学[M].北京:石油工业出版社,1996.98～116
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5 MiddletonGV .Experimentsondensityandturbiditycurrents:Ⅲde positionofsediment[J].CanadianJournalofEarthSciences,1967,4:475～505
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