准噶尔盆地克—百逆掩断裂带上下盘储层差异性及其形成机理

The Formation Mechanism of Reservoir Differences between the Hanging Wall and the Foot Wall of Ke-Bai Overthrust Fault,Junggar Basin

基于岩芯、薄片和物性数据等资料,从构造演化、沉积体系时空展布、成岩作用特征及储层质量角度,对准噶尔盆地西北缘克拉玛依—百口泉地区逆掩断裂带上、下盘二叠系—侏罗系储层特征进行系统对比研究,探讨储层差异性形成机理。在断裂上盘,沉积物粒度较粗,通常为冲积扇或辫状河沉积砾岩、砂质砾岩,埋藏较浅,孔隙性较好。在断裂下盘,沉积物相对较细,通常为辫状河三角洲或扇三角洲前缘沉积砂岩,埋藏较深且孔隙性整体较差;局部层段发育沸石和长石的强烈溶蚀。通过分析认为,研究区储层埋藏史(断裂演化史)控制上、下盘储层砂体成因,决定储层现今埋深及成岩演化,影响储层次生孔隙的形成;沉积体系发育受同生的克—百主断裂控制,影响储层粒度、岩石成分成熟度、结构成熟度,决定储层原始孔隙结构发育情况。

On the basis of a large number of thin-sections,casting thin-sections,and physical property analysis of cores,the article systematically compares Permian-Jurassic reservoir differences between the foot wall and the hanging wall of the Ke-Bai overthrust fault,northwestern margin of Junggar Basin from the perspectives of structural evolution,time-space distribution of the depositional system,diagenesis evolution,and reservoir quality. The formation mechanism of reservoir differences have been discussed. The reservoir on the hanging wall is near to the provenance with coarse grain size and shallow burial depth. The lithologies are conglomerate and sandy conglomerate of alluvial fan and braided river. The compaction is weak and a large number of primary pores are well preserved. The reservoir on the foot wall is far away from the provenance with deeper burial depth and finer grain size. The lithology is sandstone of braided river delta and fan delta front. Zeolites and feldspars are intensely dissolved within some intervals. Comprehensive analysis shows that the reservoir burial history( fracture evolutionary history) controlled facies association,present burial depth,and the formation of secondary porosity in the study area. Depositional systems effected by KeBai fault had a genetic impact on the grain size,compositional maturity and textural maturity of the reservoir rocks,controlling the development of primary pore configuration.