宁东煤田李家小庄勘查区延安组岩相古地理参数特征研究

The Study of Lithofacies Paleogeography Parameters in Lijiaxiaozhuang Exploration area of Ningdong Coal field under System Tracts

在宁东煤田李家小庄勘查区中侏罗统延安组等时层序地层格架下,以三级层序为单位,从地层厚度、砂体厚度、泥岩厚度、砂泥岩比及煤层厚度多因素条件出发,进行岩相古地理参数特征研究。结果表明:研究区延安组可划分为3个三级层序,在SIII1沉积时期,地层沉积厚度大,砂泥岩比不高,沉积微相基本属于冲积河道,煤层的沉积中心处于物源供给较丰富且漫滩沼泽和泥炭沼泽相对发育的地区,形成的煤层厚度在4～14m;SIII2沉积时期,砂体厚度明显大于SIII1层序时期沉积的砂体,冲积河道(分流河道)微相比较发育,煤层总厚度在4～6m;SIII3沉积时期,区内地层沉积中心反映不明显,砂体总厚度明显增厚,砂泥岩比整体大于40%,冲积河道(分流河道)的发育范围明显增大,由于泥炭沼泽发育程度减弱,煤层不发育。

Take the Yanan formation Mid-Jurassic of Lijiaxiaozhuang exploration area of Ning Dong Coal field as example,at the guide of the isochronous stratigraphic framework,Using the third-order sequences as the mapping unit,under the guide of lithofacies paleogeography characteristics affecting facts including formation thickness/sand body thickness/mudstone thickness/ratio of sand to shale /coal seam thickness,the Lithofacies paleogeography Parameters have been studied under the tract condition.The results show that,Yanan formation Mid-Jurassic of Lijiaxiaozhuang exploration area can be divided into 3 third-order sequences,at the period of SIII1,formation thickness is high,and the ratio of sand to shale at a proper state,alluvial channels microfacies is the main sedimentary facies,the sedimentation center of coal seam correspond with the abundant material supply,coal seam thickness is about 4～14m,show the highest thickness in 3 third-order sequences.At the period of SIII2,sand body thickness is higher than that in SIII1 period,alluvial channels（Distributary Channel） microfacies distribution is stronger and the peat thickness is relative higher than that in SIII1 period,the coal seam thickness is about 4～14m.At the period of SIII3,the sedimentation center is not clearly,sand body thickness is highest than that in 3 third-order sequences,the ratio of sand to shale is about 40%,and the distribution range of alluvial channels（Distributary Channel） microfacies enlarged obviously,with the decreasing of mire developed area,coal seam is not developed at this period.