砂质纹层的发育特征及对页岩储层物性的影响--以鄂尔多斯盆地南部中生界延长组为例

摘要

Through the observation and measurement of outcrops and cores,this paper analyzes the characteristics of sandy laminar of the upper triassic Yanchang Fm in southern Ordos basin,and using scanning electron microscope ( SEM)and X-Ray diffraction( XRD)to observe and analyze the rock mineral characteristics of sandy laminar and pure shale. In order to analyze the effect of sandy laminar on the shale reservoir property,this paper uses pulse de-cay method to test the porosity and permeability of the shale and sandy laminar. The results show that sandy laminar can increase the porosity and horizontal permeability of shale reservoir,clastic particles such as quartz and feldspar in sandy laminar can form a supporting structure which is favourite to preserve the primary pores,and paulopost dis-solution can increase the porosity of shale reservoir to some extent. These clastic particles can also increase the shale brittleness,which is benefit for shale fracturing. The bedding surface of the shale and sandy laminar increases the horizontal permeability of shale reservoir. So we should pay attention to the sandy laminar of the shale reservoir in the shale gas exploration and development process.%通过露头剖面、岩心观察和测量，分析了鄂尔多斯盆地南部中生界页岩中砂质纹层的发育特征，并利用扫描电子显微镜和XRD定量分析技术，分别观察分析了砂质纹层和纯页岩层的微观特征和岩石矿物学组分。在此基础上，为了分析砂质纹层对页岩储层物性影响，用脉冲衰减法对砂质纹层和纯页岩层的孔隙度和渗透率进行测试，结果表明，页岩中发育的砂质纹层增大了页岩孔隙度和水平渗透率：砂质纹层中含有石英、长石等碎屑颗粒，在成岩压实过程中形成的支撑结构有利于原生孔隙的保存，后期溶蚀作用也在一定程度上增加了页岩储层的孔隙度，这些碎屑颗粒也增加了整个页岩层系的脆性，有利于页岩后期的压裂；砂质纹层与页岩之间形成的层理面增大了页岩储层的水平渗透率。因此，页岩气的勘探部署和后期开发过程中要重视砂质纹层的研究。