库车坳陷克深5井区巴什基奇克组应力垂向分层特征

Characteristics of Vertical Zonation of Bashijiqike Reservoir by Stress Intervals in Wellblock Keshen-5 in Kuqa Depression,Tarim Basin

通过对岩心、普通薄片、铸体薄片、扫描电镜、高压压汞等实验数据的分析,对库车坳陷克拉苏构造带克深5井区巴什基奇克组不同应力段岩石学特征、储集空间类型、物性以及孔隙结构特征展开对比分析。不同应力段岩性相似,均以方解石胶结的岩屑长石砂岩为主,但张性应力段碎屑颗粒以点状和点-线状接触为主,过渡段碎屑颗粒以线状接触为主,压扭应力段碎屑颗粒呈定向排列;不同应力段储集层基质孔隙类型存在差异,从张性应力段到压扭应力段,储集层平均孔隙度逐渐变小,平均渗透率则逐渐变大。不同应力段孔隙结构存在差异,张性应力段储集层毛细管压力曲线以Ⅰ类和Ⅱ类为主,排驱压力、中值压力低,进汞饱和度高,平均孔喉半径大,喉道均匀,连通性好;而压扭应力段储集层毛细管压力曲线以Ⅳ类为主,平均孔喉半径小,孔喉分选、连通性差,排驱压力、中值压力受微裂缝影响,分布不规律;过渡段储集层特征基本介于张性应力段和压扭应力段之间。研究结果明确了克深5井区储集层垂向分层性,改变了按岩性段对储集层特征展开对比分析的传统方法。

Through analysis on the experimental data of core, common thin section, cast thin section, SEM and high-pressure mercury injection, correlation and analysis on lithological features, reservoir space types, physical properties and pore structures are carried out for each stress intervals of Bashijiqike formation in Wellblock Keshen-5 in Kelasu structural belt, Kuqa depression. The result shows that different stress intervals are similar to each other, all of which are dominated by lithic feldspar sandstone cemented by calcite, but the clastic particles in extensional stress interval are mainly spot and spot-line contacts and that in transitional interval are dominated by line contact, that in transpressional interval are in directional alignment; matrix pore types are different in different stress intervals, the average reservoir porosity gradually decreases and the average permeability becomes larger from the extensional stress interval to the transpressional interval. The pore structure varies in different stress intervals, the capillary pressure curves of the reservoirs are mainly Type I and 11 in the extensional interval, which is featured with low displacement pressure and median pressure, high mercury-intrusion saturation, large average pore-throat radius, even pore throats and good connectivity; the capillary pressure curves of the reservoirs are dominated by Type IV in the transpressional interval, which is featured with small pore-throat radius, poor pore-throat sorting and connectivity, irregular distributed displacement and median pressures due to the influence of microcracks; the reservoirs in transitional interval have moderate features between extensional and transitional intervals. The results of the study verify the vertical zonation of Bashijiqike reservoir in Wellblock Keshen-5, and change the conventional method for lithology-based reservoir correlation and analysis.