Abstract: The low permeability formation characters of different oil fields are much different，which affects the ability flowing through porous media and development effect.Constant rate Hg injection test，NMR test，threshold pressure gradient to flow test and clay analysis are carried out on low permeability cores from Daqing and Changqing Oilfields to study their formation properties and characters of flow through porous media.Research results indicate that the main flow throat is the main controlling factor for ability flowing through porous media.The amount and types of clay minerals and movable fluid saturation decrease the effective size of flow channels especially for Daqing low permeability formation with high amount of clay.For Changqing and Daqing Oilfields，even with the same gas permeability，the main flow radium and movable fluid saturation of low permeability reservoirs in Changqing are much bigger than those in Daqing，while the threshold pressure gradient of low permeability reservoirs in Changqing is much lower than that in Daqing，which indicates why it is easier to develop low permeability reservoirs in Changqing than to develop the low permeability reservoirs in Daqing.

Key words: low permeability, reservoir, throat, movable fluid, flow through porous media