Abstract: Searching for residual oil is important for old oil field. By studying micro structure of oil reservoir, fault and the sealing,the paper points out the character of micro structures is very important factor to control distribution of residual oil. Based on the study, two potential areas were defined, (1) the positive micro structures, including the positive micro structures in low posi-
tion;(2) the micro structures by fault, including sealing, hold and barrier of fault. By penetration of reservoir, it was indicated that determining the rich area of distribution of residual oil by micro structure is a valuable method; fault and micro structure of oil reservoir is very important factor to control residual oil. The positive micro structures of oil reservoir and fault are
the area where residual oil is concentrated.

Key words: micro structure, residual oil, fault sealing, L oil field