Abstract: There are extensive bituminous sandstones in Silurian in Tarim Basin,which means substantive hydrocarbon was accumulated in Silurian in geological time and which also illustrates the palaeo reservoir accumulated early in Silurian was badly destroyed.To correctly evaluate remaining resources of Silurian and carry out further exploration in Silurian,it is very important for us to fully understand the scale of palaeo reservoir in Silurian.The distribution characteristics,forming process and mechanism of Silurian bituminous sandstones and the forming pattern of early Silurian reservoir are established,and the study results show that palaeo reservoir in Silurian are not so large on scale as imagined and not giant selfcontained reservoir,there are only some big pools distributing in partial uplifts of precarboniferous.

Key words: Tarim Basin, Silurian, bituminous sand, petroleum accumulation model, scale of palaeo reservoir