Fractal pore measurement of 28 samples collected from Upper Jurassic sandstone were made using a statistical analysis of structural features on fracture surfaces of SEM pictures.The fractal pore measurement indicates that there are two types of fractal pores. The depositional fractal pores and diagenetic fractal pores. The depositional fractal pores are formed of original irregular grain surfaces during deposition. The fractal dimension is less than 2.50

the fractal porosity is generally less than 5%

the fractal pores amount to 15% of the total pores. The diagenetic fractal pores resulted from authigenetic clay minerals

qaurts and dissolution of fieldspars. The fractal dimension of those fractal pores is greater than 2.50

the fractal porosity is usually higher than 5%

and the fractal pores are more than 50%-80%. No fractal pores caused by carbonate cements could be found. Almost all the pores in mudstone are fractal pores while there is no fractal pores in diabase.