Abstract: Study on distribution of remaining oil in target block is conducted by using Eclipse software for improving water flooding efficiency. Results show that distribution of remaining oil is affected by different factors during different development stage, it is affected mainly by difference of formation physical property during expansion driving phase and by formation inhomogeneity and well spacing pattern during water flooding phase. Present remaining oil of this block mainly distributes in the areas with lower permeability, imperfect flooding pattern or blocks in oil layer and non-essential streamline region of injection well. Development effect of Main Unity reservoirs can be effectively improved by locally lowering down well space, adjusting layer system and water flooding pressure maintenance. Development mode of perimeter waterflooding is superior to intracontour waterflooding in dealing with fault block reservoirs like Main Ghazal which has well physical properties, good communication and suitable size. Next stage optimized development plan of Main Unity reservoir is proposed and recovery will be 4.73% higher contrasting to current well spacing pattern.

Key words: remaining oil, development stage, distribution, remaining oil development strategy