鄂尔多斯盆地东北部山西组下段基准面旋回与聚煤作用

Coal-accumulation of lower member of Shanxi Formation in northeastern Ordos Basin

依据基准面旋回的原理,应用露头、钻井和测井资料,通过沉积相分析、基准面对比和密集数据控制的平面制图,研究了鄂尔多斯盆地东北部山西组下段煤层在基准面旋回中的位置、煤层在纵向和横向的变化和平面分布。结果表明:煤层的形成与基准面旋回和相分异作用有关,煤层形成于短期基准面上升的晚期。煤层的分布与河道呈互补关系。在远离河道的泥炭沼泽区,煤层厚度大,灰分低,所夹矸石层少。向河道方向,煤层分叉变薄,灰分高,向碎屑岩过渡。从山23到山21,厚煤层的分布总体上呈向北退却的趋势,反映了山西组下段构成一个中期基准面上升的过程。

The coal accumulation of lower member of Shanxi Formation,northeastern Ordos Basin has been researched according to principle of base level cycle on basis of analysis of outcrops, core description, and well log, and sedimentary facies analysis, base level correlations condenses data controlling mapping were adopted. Coal forming has a dose relation to base level cycle and facies distribution,coal formed latter stage of short-term base level ascending cycle. Coal measttres distribution has a complementary relationship with distributary channel. In peat swamp far from distributary channel,coal layer has great thickness,with lower ash content,and lack of waste rock interlayer. Near the distributary channel,coal layer divarieation and pinch-out with high ash content, and transition to elastic rock. From Shah23 to Shan21,thick coal layer has a trend of retreat towards north,reflect that lower member of Shanxi Formation constituted mid-term base level ascending cycle.