基于成因类型的砂质辫状河泥岩分布模式——以山西大同侏罗系砂质辫状河露头为例

山西大同云岗组砂质辫状河以砂质沉积物为主,发育河道、心滩、边滩3种典型岩相组合,储集性能好,通常可作为良好的油气储层,但是其内部仍然存在泥质隔夹层.通过对山西大同体罗系砂质辫状河典型露头的实测和分析,总结出砂质辫状河沉积中4种不同成因类型的泥岩,分别为泥塞、水道底部滞留泥、侧积披覆泥和洪泛泥.以单期水道为基本单元,建立了基于成因类型的砂质辫状河泥岩分布模式,限定了各成因类型泥岩的展布范围,泥塞、水道底部滞留泥和侧积披覆泥的分布受控于单期水道,洪泛泥的分布受控于活动水道,为有效预测砂质辫状河储层中泥岩的几何形态、空间分布规律及规模提供了概念模式.

Pattern of Genesis-based Mudstone Distribution for Sandy Braided River: A Case Study of Sandy Braided-River Outcrop,Datong,Shanxi Province,China

Sandy braided river of Yungang Formation which is dominated by sands is composed of three typical lithofacies associations of channel,channel-bar and point bar.It as good oil/gas reservoirs has good reservoir properties,but there is muddy interlayer inside the sandy braided river deposits.According to measurement of typical outcrops of Jurassic sandy braided river in the Datong city,Shanxi province,we identify four genetic types of mudstone in the sandy braided rive deposits,i.e.mud plug,channel lag mud,lateral accretion mud,and flood plain mud.According to genesis types,we take the channels of single stage as basic unit to setup the distribution model of mudstone in the sandy braided river,limit the distribution range of mudstone of each genesis type.The distribution of mud plug,channel lag mud and lateral accretion mud is constrained by channels of single stage,while the distribution of flood plain mud is controlled by active channel zones.The establishment of distribution pattern can provide a concept model for the effective prediction of the geometric shape,rules and scales of spatial distribution for mudstone in reservoirs of sandy braided river.