Abstract: A study was conducted on the model of primary migration of oil and gas. It is believed that source rocks still have certain permeability. The higher the permeability, the stronger the ability of primary migration of oil and gas out of source rocks is. And the lower the permeability, the stronger the ability to seal the reservoir pressure of source rocks. The heterogeneity and micro-fissures in source rocks are unfavorable to primary migration of oil and gas, which retained some oil gas within the source rocks forever as micro-reservoirs. Thinner source rocks have a lower a potential capacity of hydrocarbon generation, a higher capacity of hydrocarbon drainage and a lower capacity of hydrocarbon accumulation. However thicker source rocks have a higher potential capacity of hydrocarbon generation, a lower capacity of hydrocarbon drainage and a higher capacity of hydrocarbon accumulation.

Key words: rock, source rock, hydrocarbon migration, model, permeability, formation pressure