The Paleozoic marine carbonates are the main exploration targets in both Tarim and Williston basins.Based on a comparative analysis of both tectonic-depositional setting and conditions for the formation of hydrocarbon accumulations

this paper discusses the similarities and differences of hydrocarbon accumulation in the Paleozoic marine carbonates of the two basins.Williston Basin locates within the large North America Plate with relatively stable tectonic setting.The sedimentation within the basin was mainly controlled by eustasy.In contrast

Tarim Basin locates in the much smaller Tarim Plate and experienced frequent and intensive structural deformations.As a result

the sedimentation within the basin was mainly controlled by the tectonic movements.Williston Basin has high-TOC effective source rocks

good porous-type reservoirs and evaporite cap rocks

while Tarim Basin has high-mature to overmature source rocks

karst and dolomite reservoirs

and mudstone and evaporite cap rocks.Different kinds of traps are developed on the paleo-highs in both basins

which constitute the main carbonate play fairways.Williston Basin has multiple evaporite sequences

which makes it possible to effectively apply the petroleum system concept to the basin.In comparison

the hydrocarbon accumulation system concept can provide effective guidance for the hydrocarbon exploration in basins such as Tarim Basin featuring in multiple source rocks

multiple kitchens and multiple episodes of hydrocarbon charging.The favorable reservoir-seal assemblage in Williston Basin is dolomite reservoir and evaporite seal.The comparative analyses indicate that the favorable carbonate play fairways are the areas with the assemblage of the Lower-Middle Cambrian dolomite reservoirs and the Middle Cambrian evaporite seals in the Bachu and Tazhong areas.