塔里木盆地北部下寒武统肖尔布拉克组前积体特征及其形成机理探讨

Discussion on the characteristics and formation mechanism of carbonate progradation body of the Lower Cambrian Xiaoerbulak Formation in northern Tarim Basin,NW China

为刻画塔里木盆地北部下寒武统肖尔布拉克组前积体的迁移方向、空间分布、成因机理以及与储层发育的关系,基于最新处理的二维地震大测线和其间的加密小测线共45条测线的地震剖面解释追踪,对前积体进行了精细刻画,探讨了其形成过程、影响因素及其与有利储层发育的关系。结果显示:塔里木盆地北部肖尔布拉克组共发育5个垂向上相互叠置、平面上由南西向北东依次推进的前积体。在地震剖面上,单个前积体呈S形透镜状,中间厚而前后两端薄,内部反射结构表现出厚的主体部位呈较弱的杂乱反射,较薄的两端则呈较强的平行-亚平行反射。前积体的形成受早寒武世基准面变化的控制,是宽缓的斜坡地形和持续的海平面下降引起沉积可容纳空间减小并不断向海迁移的结果,并在后期台缘带发育部位逐渐收敛终止。前积体的主体部位是高能丘滩相优质储层的有利发育区,而其后侧的微生物岩则可形成生物格架溶蚀孔洞型良好储层。

Based on the seismic profile interpretation and tracking of 45 newly processed 2D large seismic lines and the infused small seismic lines,the migration direction and spatial distribution of the Lower Cambrian Xiaoerbulak Formation progradation bodies in the northern Tarim Basin are described in detail and its formation process,genetic mechanism,influencing factors and the relationship between the formation and favorable reservoir development are discussed.The results show that there are five vertical overlapped progradation bodies advancing from SW to NE in the north Tarim Basin.In the seismic profile,the single progradation body occurs as S-shaped lens,with thick middle parts and thin ends.The internal reflection structure shows weak chaotic reflection in the thick main part,and strong parallel-subparallel reflection in the thin ends.It is revealed that the formation of progradation bodies was controlled by the change of early Cambrian datum level,as a result of the wide and gentle slope topography and continuous sea level drop,which caused the decrease of the sediment space and continuous seagoing migration,and gradually converging and ending in the late platform margin zone.It is considered that the main part of the progradation bodies is the favorable development area of high energy dune facies reservoir,and the microbialite behind it can form a good reservoir with biological framework dissolution pore space.