Abstract: In long-term waterflooding developed oilfields,the long-term immersion and displacement of developing fluid to reservoirs made minute spaces connecting multiple micropores with porethroats dynamically changed,and rock framework,porethroat network and clay mineral also changed dynamically.These changes affected the distribution of underground residual oil.Aimed at the delta reservoirs in the 8th sand formation of the Sha-2 Member in shengtuo oilfield,a dynamic micromodel of reservoirs was established from rock framework,porethroat network and clay mineral three respects,and the relationship between microchanges and residual oil studied.It was suggested that these changes were dynamic and continuous,and made the distribution of residual oil further complicated.