Keywords: 
• primary migration /
• generation and expulsion of hydrocarbon /
• isotopic fractionation /
• oil-source correlation /

Abstract: There exist possible isotopic fractionation effects in generation-expulsion process of terrestrial source rocks. Primary cracking of kerogens, secondary cracking of hydrocarbons and primary migration of hydrocarbons can lead to possible isotopic fractionations. In the following primary migration simulation deuterated normal C₁₅( n-C₁₅D₃₂) was added into different source rocks to study the isotopic fractionation in primary migration. The results of simulation experiment showed that there are differences between δ¹³C values of expelled n-C₁₅D₃₂ and extractable n-C₁₅D₃₂ from different layers of desmocolliniterich coal (about 3‰ in less than 10cm distance, but there is no obvious isotopic fractionation in primary migration of fusinite-rich brown coal and mudstone.
Specific surface area in desmocollinite-rich coals is large and the pore structures are very complex, furthermore, oil window of type Ⅲ kerogens is wide, all these factors make the generation-expulsion process of desmocolliniterich coals very complicated and it is easier to have isotopic fractionation. Thus, isotopic fractionation effects should be considered in oil-source correlation of coal-sourced oil.