塔里木盆地雅克拉断凸周缘阳霞组沉积相

Sedimentary Facies of Yangxia Formation Around Yakela Fault⁃Bulge in Tarim Basin

塔里木盆地北部雅克拉断凸周缘侏罗系是重要的油气勘探层位,主要发育断凸为物源的近源冲积扇-扇三角洲沉积体系,但该模式难以解释雅克拉断凸南部侏罗系大规模砂体发育的原因。在雅克拉断凸构造演化分析的基础上,利用地震、岩心、储集层等资料,开展沉积相特征的综合分析,确定雅克拉断凸周缘侏罗系阳霞组沉积相空间分布规律。雅克拉断凸在侏罗系沉积期整体具有西高东低的特征,西部受剥蚀,东部在阳霞组沉积晚期为准平原化状态,其沉积体系主要包括2部分:一部分为雅克拉断凸西部物源,形成大量沿断凸呈裙边分布的近源扇三角洲沉积体系;另一部分为南天山物源,在雅克拉断凸东部形成了自北向南延伸的浅水辫状河三角洲沉积体系。从储集层特征上看,扇三角洲沉积体系岩性较粗,主要为砾岩和含砾中—粗砂岩,结构成熟度和成分成熟度低,物性差;辫状河三角洲沉积体系岩性主要为含砾中—细砂岩,搬运距离长,结构成熟度和成分成熟度较高,物性较好。阳霞凹陷东部地区阳霞组可能成为有利的勘探目标区。

The Jurassic strata in the areas around the Yakela fault⁃bulge in the northern Tarim basin are critical targets for hydrocarbon exploration,where a near⁃source alluvial fan-fan delta system with the fault⁃bulge as a provenance is developed.This cannot explain the extensive development of the sandbodies in Jurassic in the southern Yakela fault⁃bulge.Based on the analysis of the tectonic evolution of the Yakela fault⁃bulge,together with the seismic and core data and the reservoir characteristics,a comprehensive analysis was conducted on the sedimentary facies to determine the spatial distribution patterns of the sedimentary facies in the Jurassic Yangxia formation around the Yakela fault⁃bulge.It is found that during the Jurassic deposition the Yakela fault⁃bulge as a whole was higher in the west than in the east,with erosion occurring in the west and a peneplain state in the east at the late stage of Yangxia formation deposition.The sedimentary system primarily comprises two parts:one sourced from the western Yakela fault⁃bulge,forming an apron⁃like distribution of the near⁃source fan delta deposits along the fault⁃bulge;the other sourced from the southern Tianshan Mountains,forming a braided river delta system extending from north to south in the eastern Yakela fault⁃bulge.From the perspective of reservoir characteristics,the fan delta system is characterized by coarse lithology,mainly including conglomerates and gravel⁃bearing medium-coarse sandstones,with low textural and compositional maturities and poor physical properties.In contrast,the braided river delta system predominantly consists of gravel⁃bearing medium-fine sandstones,and records a long transport distance,with high textural and compositional maturities and good physical properties.The Yangxia formation in the eastern Yangxia sag may be a potential favorable exploration target.