Abstract: Based on series compatibility test of formation water of 3 low permeable reserviors with all kinds of alkaline solution,combined with reservior injury assessment by the way of static and dynamic states,this paper analysed injury mechanism of well drillong liquid to reserviors and suggested some requirements of well drilling liquid for protecting reserviors.It was suggested that injury extent of all kinds of external fluid to reserviors should be comprehensively evaluated at the same time of doing core flowing test,then the treatment reagent for well liquid with better compatibility can be selected.