准噶尔盆地东部侏罗系西山窑组层序控制下的聚煤规律研究

Sequence Stratigraphic Characteristics and Coal Accumulation Model in Xishanyao Formation,East of Junggar Basin

准噶尔盆地东部地区侏罗系煤炭资源丰富,其中西山窑组是主力含煤层系,具良好的勘探前景。通过钻井资料、测井相特征及岩石组合类型综合分析,明确研究区西山窑组层序构成及层序演化,并对该时期层序控制下的聚煤规律进行了系统研究。结果表明,西山窑组作为一个三级层序,主要沉积于温暖、潮湿的前滨-浅湖-泥炭沼泽环境,其内部进一步识别出低位体系域、湖扩体系域和高位体系域。低位体系域时期不利于泥炭沼泽的持续发育和形成广泛分布的厚煤层;湖扩体系域时期,湖平面不断上升,为泥炭的生成和保存提供了良好条件,该时期研究区西部煤层较厚,由西向东煤层逐渐分叉减薄,同时由北向南逐渐分叉和减薄;高位体系域时期,煤层由西向东厚度逐渐减小,数量也逐渐减少,由南向北煤层分布较为稳定,该时期厚度较大的煤层主要发育于底部且横向上分布较稳定。湖扩体系域时期石树沟凹陷中北部和梧桐窝子凹陷中西部及高位体系域早期石树沟凹陷中南部可作为研究区西山窑组煤层重点勘探地区。

Jurassic Formation in Eastern Junggar Basin has rich coal resources and has a good exploration prospects.Developed in Middle Jurassic series,Xishanyao Formation is main coal series in whole Jurassic.Based on series of data concerning drill information,well log and rock assemblage type,it is considered that Xishanyao Formation forms in warm and wet Foreshoreshallow lake-peat bog environment.As a third-order sequence,Xishanyao Formation further can be grouped into Lowstand System Tract （LST）,Lake Expanding Systems Tract （EST） and Highstand System Tract （HST）. The study shows that sequence evolution has obvious control effect on coal accumulating. Due to rapid uplift of basin peripheral that cause rapid decline in lake level, Lowstand System Tract is not conducive to sustained development of peat swamps and the formation of widely distributed thick coal seam. While as whole basin subsidence and rising lake level in EST, it provides a good condition on the generation and preservation of peat.Furthermore, the coal seams are thick in EST and characterized by thinning coal seams from west to east, and also from north to south.Basin tectonic activity is relatively stable in HST and characterized by thinning coal seams from west to east and in the west region of Heishan uplift. Coal seams distribution is relatively stable from south to north.At the same time,the coal seams that development in the bottom of liST are thicker and more stable on the transverse distribution.