鄂尔多斯盆地东南部上古生界致密砂岩储层特征及主控因素分析

Analyses on Characteristics and Main Controlling Factors of Tight Sandstone Reservoir on the Upper Paleozoic in Southeastern Ordos Basin

鄂尔多斯盆地上古生界是我国致密砂岩气勘探开发的代表层位,盆地东南部相比于盆地北部勘探程度较低,但也显示出良好的油气勘探前景。本溪组、山2段、山1段和盒8段为研究区上古生界主要的致密砂岩发育层段。结合大量的钻井资料、岩芯观察、岩石薄片、扫描电镜以及储层物性测试数据,对鄂尔多斯盆地东南部上古生界致密砂岩储层主要储层段的沉积环境与分布规律、储层岩石学特征、储集空间、成岩作用、物性特征等进行了分析研究,最终得出研究区从本溪组到盒8段,砂体发育规模逐渐增大;砂岩储层的岩石类型以中~粗粒石英砂岩和岩屑石英砂岩为主,岩屑砂岩次之;储集空间主要为溶蚀孔、残余粒间孔与微裂缝,其中溶蚀孔是最主要的储集空间;主要的成岩作用类型主要有压实作用、胶结作用、交代作用、溶蚀作用及破裂作用。成岩作用,沉积环境和物源等因素共同控制着致密砂岩储层的发育。

Ordos Basin Upper Paleozoic is a presentational layer of tight sandstone gas exploration and development in China.Compared to the northern of the basin,exploration degree of the southeast area in the basin is lower,but also shows good prospects for tight sandstone gas exploration.Benxi Formation,the second member of Shanxi Formation,the first member of Shanxi formation and the eighth member of Shihezi Formation are main sandstone reservoirs in the study area.Combined with a large number of drilling data,drill-core samples observation and study on rock thin section,cast section,SEM and the physical property analysis of reservoir,the depositional environment and distribution of sandstone reservoir of Southeastern Ordos Basin Upper Paleozoic and the petrology characteristic,reservoir space and so on had been taken into analysis and research.We discussed the main factors which influence the development of tight sandstone reservoir in the study area.The research shows that from Benxi Formation to the eighth member of Shihezi Formation,sandbody scale increases gradually;the sandstone reservoir rock types is coarse grain sandstones quartz sandstone and lithic quartz sandstone,followed by lithic sandstone;reservoir space is dissolved pores,followed by residual intergranular pores and microfractures.The diagenesis of the study area mainly includes compaction,cementation,metasomatism,dissolution and fracturing.The diagenesis,sedimentary environments and provenance jointly controlled the development of tight sandstone reservoir.