The Diagenesis Of Sandstone Of The Upper Paleozoie, Da-22 Well Field Of Tabamiao Area, North Ordos Basin

This is mainly talk about the diagenesis characteristics of sandstone of Upper Paleozoie, Tabamiao Area of North Ordos Basin. About 29 thin sections were used to analysis the detrital and authigenic mineral composition and content. The distribution and paragenetic sequence of authigenic minerals has been study.Most studied Upper Paleozoic sandston are characterized by have great amount of fragment, which mainly constitute of phyllite and mudstone. So that, the sandstone have undergo strongly compaction, and are densification in very early. The relatively higher content of fragment may related to the metamorphic source region, and also were influenced by coal strata during diagenesis.The carbon cements can be divided into different type accord to the paragenetic sequence and morphologies. The C-I type calcite, including C-Ia and C-Ib, occurs abundantly in intergranular pore, which formed in early diagenesis. The C-Ia type calcite is abundant in the lower part of Taiyuan formation, which may formed in BSR(bacterial sulfate reduction) zone. The form of C-Ib type calcite were relate to organic acids which were released by peatification of coal strata. C-II type calcite were precipitation after the deformation of plastic fragment, which may related to carbon dioxide were formed by coalification of coal. It is not clear about the formation of DI-type dolomite, but may formed in deep condition. D-II type dolomite may related to mixed marine-meteoric water in coastal.There are two type of quartz cement(type Q-1,2 ). The Q-1 type quartz cement has well euhedral which may related to the dissolution of sandstone. Q-1 type quartz has anhedral may indicated to strong compaction which caused restriction of space for the precipitation of quartz.Two phases of dissolution were recognition based on the characteristics of secondary porosity. According to the evolution process of coal, we proposed that the first phase of dissolution were relate to organic acids which were released by peatification of coal strata during early diagenesis, and the first phase may related to carbon dioxide were formed by coalification of coal...