CHARACTERISTICS OF UPPER PALEOZOIC SANDSTONE RESERVOIR IN HANGJINQI AREA OF ORDOS BASIN

The characteristics of upper paleozoic sandstone reservoir in Hangjinqi area of north Ordos Basin were investigated by the methods of core analysis, scaning electron microscope, isotope analysis and log data.The lithology of upper paleozoic sandstone reservoir is complicated which the litharenite arkose sandstones, quartz sandstone,and lithic sandstones are founded. And there are some clay minerals such as montmorillonite, dickite, etc in the northeast of area.The pore space of reservoir mainly includes the primary residual intergranular pores and secondary intergranular pores. The porosity of upper paleozoic sandstone reservoir is medium and the permeability is low, and the pore texture is not preferable, which with high displacement and saturation median point pressure, small pore throat radius, poor pores sorting and coarse-fine skewness. Structural fractures and microfractures formed well which played important role in gas migration and accumulation or reserving and permeating. According to the lithology and petrophysical properties of reservoir and pore texture parameters,upper paleozoic reservoir was classified into four types.The type Ⅰ is the best reservoir in researched area,and the type Ⅱ and Ⅲ are the main reservoir, which are chief reservoir for exploration and production.