Abstract: The tight sandstone gas reservoir in western Sichuan is rich in reserves, but there is a phenomenon of wellbore effusion and serious reservoir damage, which affects the development efficiency. Understanding the damage mechanism of wellbore effusion reservoir is the premise and foundation to fundamentally solve the damage of effusion reservoir. In this paper, aiming at the damage problem of wellbore liquid accumulation reservoir in gas wells, quantitative evaluation experiments of wellbore liquid accumulation reservoir damage are carried out to analyze its damage mechanism. The results show that the reservoir water-sensitive minerals are easy to react with liquid; and small and medium pores, resulting in high capillary pressure, and in serious wellbore effusion damage. When the wellbore pressure increases 1 MPa, the reservoir damage increases about 6%. The damage degree of foaming agent to the reservoir increases with the increase of concentration, and the damage to the formation caused by foaming agent and condensate oil is greater. When the concentration of foaming agent is greater than 0.5%, the damage degree to the reservoir can reach more than 90%. The results provide a scientific basis for revealing the damage mechanism of wellbore effusion reservoir in tight sandstone gas reservoir in western Sichuan.

Key words: West Sichuan gas reservoir, tight sandstone, wellbore liquid loading, formation damage, evaluation mechanism