19 / 2021-11-30 13:48:46

Characteristics of clay minerals and its effect on the resevoir in the He-8 Member of Tianshengqiao Section,Fugu area,the northeastern Ordos basin（report）

Clay minerals; Tianshengqiao section; He-8 member; Sedimentation mechanism; Reservoir

Clay minerals are of great significance to the prediction of high quality reservoirs in tight sandstone. In the present study, the characteristics and precipitation mechanism of clay minerals in the He-8 member of the Tianshengqiao section in Fugu were studied by the methods including thin section, scanning electron microscope and X-ray diffraction analysis. Based on these, we attempt to discuss the relationship between the distribution of clay minerals and reservoir quality. He 8 member contains more altered tuffaceous feldspar lithic sandstone and lithic feldspar sandstone. The main types of clay minerals are kaolinite and chlorite. Kaolinite is mainly the product of alteration of tuff under the influence of acidic fluid, chlorite is mainly produced in the form of coating, and some of it is the alteration of biotite and tuff, filling in the intergranular pores. The influence of clay minerals on the reservoir has two-sideds. When the kaolinite content is less than 5%, it is beneficial to the development of the reservoir, while excessive kaolinite may block the pores. The existence of chlorite-coatings conducive to the development of pores, and the chlorite produced by pore filling will block the pores. The quantitative calculation of porosity shows that the clay minerals have negative effects on the reservoir, and kaolinite is more important than chlorite, which is the main clay mineral affecting the reservoir.