鄂尔多斯盆地吴起地区延长组长6储层特征及其控制因素

吴起地区长6油层组是一套典型的致密油产层，查清该储层的微观特征、分析影响储层发育的控制因素，有利于阐明其对致密油富集的影响。利用薄片鉴定、孔渗测试、铸体薄片、扫描电镜及高压压汞等手段，研究长6储层岩石学特征、物性及孔隙特征、孔隙结构特征及储层类型，并分析成岩作用对储层发育的影响。结果表明：该地区长6油层组的岩石类型主要为长石砂岩，孔隙度为6%～12%，平均为9.45%；渗透率为0.05～0.50 mD，平均为0.34 mD。储集空间类型主要包括残余粒间孔和溶蚀孔，具有4种不同的孔隙结构，它们的孔喉分布范围和频率稍有差异，Ⅰ类样品大孔隙较多，峰值孔喉半径为3～ 5 μm，孔喉连通性好，Ⅱ，Ⅲ类样品次之，Ⅳ类样品最差。吴起地区长6油层组成岩作用阶段总体处于晚成岩A期，胶结作用主要有硅质胶结、黏土矿物胶结和碳酸盐胶结。其中绿泥石胶结更多地支撑保护了孔隙，而伊利石胶结和碳酸盐胶结填充或阻塞了孔隙。长石、岩屑等易溶颗粒以及浊沸石等填隙物发生了溶蚀作用，形成的次生溶孔显著改善了储层物性。

Reservoir characteristics and controlling factors of Chang 6 of Yanchang Formation in Wuqi area,Ordos Basin

Chang 6 oil reservoir in Wuqi area of Ordos Basin is a set of typical tight-sandstone oil reservoirs. To find out the micro characteristics of the reservoir and analyze the controlling factors that affect the development of the reservoir are helpful to clarify its influence on the accumulation of tight oil. By means of thin section identification, porosity and permeability test,casting thin section, scanning electron microscope and high-pressure mercury injection, the petrological characteristics, physical properties and pore characteristics,pore structure characteristics and reservoir types of Chang 6 reservoir were studied,and the influence of diagenesis on reservoir development was analyzed.The results show that the rock type of Chang 6 reservoiris mainly feldspathic sandstone. The porosity ranges from 6% to 12%, with an average of 9.45%, and the permeability ranges from 0.05 mD to 0.50 mD, with an average of 0.34 mD. The main types of reservoir space include residual intergranular pores and dissolved pores, which have four different kinds of pore structures,and their pore-throat distributionare slightly different. The type Ⅰ samples have more macropores,with peak pore throat radius of 3-5 μm and good pore throat connectivity,followed by type Ⅱ and type Ⅲ samples,and the type IV sample is the worst. The Chang 6 reservoir in Wuqi area is mainly in the late diagenesis stage A. The cementation mainly includes siliceous cementation,clay mineral cementation and carbonate cementation. Among them,chlorite cementation supports more of the pores, and illite cementation and carbonate cementation fill or block the pores. The feldspar,cuttings and interstitials such as turbidities were dissolved,and the formation of secondary dissolved pores significantly improved the reservoir properties.