The pore structure of tight sandstone formation is very complicated, which has significant effects on the percolation of oil and gas. So, elaborate characterization is needed. The fractal geometry theory has provided an effective way for the quantitative characterization of pore structure. Based on the mercury intrusion data of the tight sandstone samples collected from FY formation in Daqing oilfield company, the multiple characteristics of pore structure in tight sandstone reservoirs are quantitatively studied by the two parameters of fractal zone and fractal dimension. The results show that the microscopic pore structure of the tight sandstone samples has multiple fractal features and the numbers of fractal zones can characterize the heterogeneity of formation. The number of fractal interval is the same as the peak value of pore radius distribution curve. The more fractal interval, the stronger the heterogeneity, and the worse the porosity and permeability of reservoir. For the same sample, the larger the pore radius for fractal zones is, the stronger the heterogeneity of pore structure is. For different samples, the larger the comprehensive fractal dimension is, the more the fractal zones are and the worse the porosity and permeability of formation become.

An effective way to describe the heterogeneity of pore structure quantitatively is provided by fractal theory,and the special pore cleat dual pore structure of coal rock makes iturgent to research further whether coal rock bears fractal feature and how to describe it. Using the present fractal feature research way and the fractal dimensions calculation way of sandstone as reference, mercury injection curvesof five pieces of coal porous media are carefully studied.The results show that the coal porous media bears fractal features in three separate zones, r<0.1 μ m ， 0.1 μ m<r<10 μ m and r>10 μ m. And for each zone,these pores are micro pores and small pores, middle pores and big pores and cleat (r>10 μ m)correspondingly. In general trend, the greater the fra ctal dimension is, the smaller the values of porosity and permeability and the worse the sorting and heterogeneity features of pores are. For different radius zones of a certain sample,the greater the fractal dimension is, the greater the heterogeneity of its pore radiusis.

Oilwater relative permeability curve reflects the law of oil and water flowing in the porous media, and the characteristics of pore structure are important factors which greatly influence the relative permeability curve.The effects of the pore structure characteristics on the permeability and the characteristics of relative permeability in F reservoir was analyzed. It is found that the absolute permeability increases with the radius of pores and sorting coefficient upgoing and decreases with the coefficient of pore structure upgoing .The irreducible water saturation and isotonic point saturation decrease with the pore radius and sorting coefficient increasing, and increase with the coefficient of pore structure increasing.The endpoint permeability of water phase increases with the pore radius and sorting coefficient upgoing, and decreases with the coefficient of pore structure upgoing. The parameters of permeability and relative permeability characteristics in this formation are in power function relationship with the micro pore structure characteristics.