Abstract: The Fault Block Pu12,a typical homogeneous massive oil pool,is in pro duction decline period with a super-high water-cut .Residual oil distribution is critical to development ad justment and production poten tial tap-ping at late development stage.Numerical simula tion through dividing the reservoir into vertically14units and laterally23×26grids achieved a reserves of 3.16million tons with a deviation of 2.4%from the actual OOIP.The residual oil distribution patterns of each oil layers were recognized to pro vide basis for further tap-ping of production potential.