Reservoir main controlling factors of Chang8 sandstones in Jiyuan and Huangling areas, Ordos Basin

There are obvious differences of reservoir physical properties of Chang8 sandstones between the Jiyuan area in the northwest and the Huangling area in the southeast of the Ordos Basin. The factors influencing intergranular and dissolution pores were discussed based on granularity, thin section and SEM analyses. In this way, the controlling factors for reservoir physical properties and the mechanism for reservoir compaction were determined. The deposition system controlled the petrologic composition of the sandstones, the content of minerals with different physical and chemical stabilities, the content of feldspar, which caused secondary porosity, and the content of minerals with different mechanical properties (rigid, semi-plastic or plastic). Depositional environment controlled the granularity and sorting of clastic compositions in reservoir. The content of detrital mud components controlled the content of authigenic clay minerals. The difference in deposition system and environment between the two areas led to the difference of intergranular and dissolution pores, and explain the obvious differences of reservoir property.