The oil pooling process in the Carboniferous Tz-4 field is quite typical in the Lower Paleozoic petro-leum system

Tarim basin.The molecule and carbon isotope geochemical behavior of oil in the field was analyzed systematically and the pooling process was reassessed based on regional sedimentology and tectonics as well as geochemical data of reservoir bitumen and fluid inclusions.The results indicate that two kinds of source kitchens(i.e.the Middle-Upper Ordovician and the Middle-Lower Cambrian) with different thermal evolution history in the central Tarim basin might have contributed to the formation of the Carboniferous Tz-4 oil pool.The C

Ⅰ

reservoir is thought to be formed by one hydrocarbon charging from a single oil source and suffered almost no geochemical alteration

whereas the C

Ⅲ

reservoir is characterized by diversified hydrocarbon sources

multiphase charging

and late modification.The results also suggest that the C

Ⅱ

reservoir has a close relationship with C

Ⅲ

reservoir

and is partly the product of C

Ⅲ

reservoir adjustment and modification.