辽河东部凹陷小龙湾地区含煤地层沉积体系特征

The Features of Coal-bearing Depositional System in Xiaolongwan Area of Eastern Sag in Liaohe Basin

小龙湾地区位于盆缘断层驾东断层和驾掌寺断层之间相对低洼地带,根据单井岩性、沉积构造等分析,沉积相类型主要为陡坡-洼陷带的扇三角洲-湖泊沉积体系。研究区沙三上亚段煤层主要分布于三角洲平原和滨湖相的泥炭沼泽中,平面上沿盆地陡坡和洼陷带呈长轴条带状排列。研究区沙三晚期处于盆地强烈断陷的回返阶段,在经历了沙三中湖泊相沉积之后,迅速过渡为浅水或水上环境,沉积相类型以三角洲平原相和河流泛滥平原相为主,形成了广泛的平原沼泽相煤层,为下一步有利勘探区。

The Xiaolongwan area is located in relatively low-lying zone between Jiadong basin-marginal fault and Jiazhangsi fault. According to the analysis of single well lithology and sedimentary structures, the type of sedimentary phase is mainly the fan delta-lake depositional system located at steep slope-depression zone. Coal seams in the upper part of Es3 in this study area mainly distribute in peat swamps of delta plain and offshore lake, which are ranged as a major axis of strips along basin slopes and depression zone in a plan view. The late of Es3 age in this study area was a return stage of intensely depression of the basin,after the lacustrine deposition of the middle of Es3 age,this area rapidly transited into shallow or on the water environments whose main types of sedimentary phases were delta plain and river flood plain. The extensive coal seams in plain-swamp phases were developed in the area, which became the main favorable area for further exploration.