鄂尔多斯盆地东南部上古生界储集砂岩的成岩作用

The diagenesis of Upper Paleozoic reservoir sandstones in the southeastern Ordos Basin

研究鄂尔多斯盆地东南部上古生界砂岩储层特征,以及不同的成岩作用类型与储集性能的关系。通过分析取芯井的岩石薄片、铸体薄片、扫描电镜、能谱分析数据,发现储集砂岩中发育有粒内溶孔、粒间孔、粒间溶孔、晶间孔、溶缝等多种孔缝类型,其中最主要的是粒内溶孔和粒间溶孔;主要成岩作用类型有压实作用、溶蚀作用、碳酸盐矿物、硅质矿物和黏土矿物的形成作用。结合不同砂岩组分与孔隙面孔率的相关性,得到如下结论:(1)压实作用是导致砂岩孔隙度较差的重要原因;(2)增加砂岩整体孔隙度最重要的是溶蚀作用;(3)碳酸盐矿物的形成会导致砂岩孔隙度减小;(4)硅质矿物会一定程度减少砂岩粒间孔;(5)高岭石的形成对增加岩石整体孔隙作用有限,水云母和绿泥石对溶孔和晶间孔的形成不利。

Samples fromthe drilling cores are analyzed through the observation of conventional thin sections,casting thin sections and as well as by SEM and energy spectrumanalysis so as to study the characteristics of U pper Paleozoic sandstone reservoir and the correlation of diagenesis and reservoirs in the southeast of Ordos Basin. It shows that intragranular dissolved pores, intergranular pores,intergranular dissolved pores, intercrystal pores and dissolved fissures develop in the reservoir sandstones,with the intragranular dissolved pores and intergranular dissolved pores as the major pore types. The study reveals that the diagenesis of sandstones includes compaction, dissolution, and formation of carbonate minerals, siliceous minerals and clay minerals. The correlation of sandstone composition and porosity indicates that compaction is an important factor leading to the worseness of porosity,while dissolution increases the porosity in the sandstone. The occurrence of carbonateminerals results in the decrease of porosity and siliceous minerals decrease the intergranular pores to some extent. The appearance of kaolin plays a limited role in the increment of porosity, while the occurrence of chlorite and hydrous mica is a disadvantage to the intercrystal pores.