宝鼎盆地晚三叠世煤系层序地层与聚煤规律

A sequence stratigraphic analysis and coal accumulation of Late Triassic coal measures in the Baoding Basin

  • 摘要: 运用层序地层学有关理论和方法,根据钻井、测井等资料,对四川宝鼎盆地晚三叠世大荞地组煤系进行了层序地层学与聚煤作用研究。共识别出12个层序界面,并将大荞地组划分出1个二级层序、3个三级层序和11个四级层序。垂向上,大荞地组二级层序格架下聚煤强度曲线总体呈先增强再减弱的趋势,且以高位体系域中期(盆地稳定断陷期SIII2)的聚煤作用最好。在该断陷盆地演化的早中期(SⅣ1—SⅣ5),主要煤层多发育于四级层序低位体系域、湖侵体系域早期以及高位体系域中晚期;至该盆地演化的中晚期,随着盆地基底沉降速率减缓,主要煤层逐渐向最大湖泛面附近迁移。

     

    Abstract: Principles and methods of sequence stratigraphy for drilling cores and well logging have been used to research these coal measures' sequence stratigraphy and coal accumulation.Twelve sequence boundaries were identified,which subdivided the Daqiaodi Formation into 1 second-order sequences,3 third-order sequences,and 11 fourth-order sequences.Vertically,the strength of coal accumulation of the second-order sequence of the Daqiaodi Formation was characterized by increased first and then decreased,with the most favorable time of coal accumulation occurring in the middle highstand system tract(SIII2).In the early of fault basin evolu-tion(SIV1-SIV5),the main coal seams' location close to the lowstand system tract,the early transgressive system tract and the middle-late stage of highstand system tract of the fourth-order sequence.In the middle-late stage of fault basin,with the reduction of the subsidence rate of basin basement and the position of the main coal seams transferred to nearly the maximum flooding surface.

     

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