Abstract: On the basis of studying thoroughly their geological conditions, this paper evaluates quantitatively the accumulation of four petroleum accumulation systems around Manjiaer sag in Tarim basin. The study shows that Tabei system is as similar as Tazhong system, while Kongquehe slope system is as similar as Tadong system in features. It is also observed that these four petroleum accumulation systems have such common characteristics as that hydrocarbons could not be expelled until they filled into source rocks completely, and the hydrocarbons drained could be mostly lost in the process of petroleum accumulations, hence only surplus hydrocarbons in excess of lost part is available for accumulation; the hydrocarbons expelled earlier is less favorable for accumulation than those expelled later; structural destruction and remained reservoir rocks are the most important reasons for hydrocarbons lost in the process of petroleum accumulations,for natural gas,migration and dispersion could be added as the other two reasons.

Key words: Tarim basin, Manjiaer sag, petroleum accumulation system, quantitative evaluation, reservoir feature