Abstract: The experiments on micromechanism of forming residual oil have been made by using microtransparent sand-packed model. The forming procedures, the micro distribution rule of residual oil and affected primary and second factors are researched by water flooding, polymer flooding and week gel flooding processes. This paper presents the classification of the residual oil into such three types as movable oil, movable oil due to some special conditions and non-movable oil. The study shows that the heterogeneity of reservoir rocks results in forming of the residual oil. The residual oil by water flooding process is mainly distributed in the un-swept area, the surface of oil-wet stone, sealed pore, micro pore, low permeability layer and partially blocked pore. The residual oil by polymer flooding process is mainly in sealed pores (non-movable oil), micropores and surface of oil-wet stone (condition movable oil). The residual oil by weak gel flooding process is in sealed pores and surface of oil-wet stone.

Key words: residual oil, micro distribution, physical simulation, water flooding, polymer, gel