Abstract: The sandstone reservoir of Ed1 in Nanpu Oilfield is severely damaged and plugged by mud in the process of drilling. There is good evidence of oil and gas while drilling, but after well completion there is no oil and gas production or the productivity is very low. Acid flowing experiment had been conducted in lab which injected acids though the damaged core under simulated subsurface conditions to analyze the permeability after acidizing. According to the result of acid flowing experiment, lithology of the rock and properties of the fluid in reservoir, multi-hydrogen acid system was chosen to dissolve the drilling fluid damage.