Abstract: Tight sandstone gas reservoirs are characterized by low porosity, low permeability, complex pore structure, and poor pore connectivity, and are susceptible to severe damage by the water blocking effect. For this reason, according to the water blocking mechanism and reservoir conditions of tight sandstone gas reservoirs, long cores corresponding to the formation were selected. Pressure loss evaluation and permeability damage evaluation experiments under different reservoir conditions and different water blocking degrees were carried out. Two concepts were proposed, namely pressure loss rate and permeability damage rate, to characterize the damage degree of water blocking effect to the pressure propagation process and reservoir permeability. The results show that: in the process of gas field development, the water blocking effect badly damages the reservoirs with poor physical properties and low gas permeability, and preventive measures should be implemented in advance; reservoirs with better physical properties and higher gas permeability can be determined whether optimization measures are needed based on the value of its pressure loss rate and permeability damage rate. For different reservoirs, the reasonable implementation of the water unblocking process is of great significance to the production and economic benefits of gas wells.

Key words: tight sandstone gas reservoir, water blocking effect, long core, pressure loss, permeability damage rate, gas well productivity