Abstract: The porous permeable strata are called carrier beds. They are the pathways for hydrocarbon migration. The transporting capacity of the carrier beds is related with the physical properties of the rocks. The better the physical property is, the stronger the transporting capacity is. Otherwise, the worse the physical property is, the weaker the transporting capacity is. Based on the analysis of the Mesozoic carrier beds in Karamay and Baikouquan area it is determined that the lower limit values of physical properties for the hydrocarbon carrier beds are not the fixed numbers. They are related with the burial depth, oil properties and the deposit conditions. The distribution of the carrier beds has a direct control on the distribution of petroleum reservoirs. Only if the traps are distributed on the carrier beds nicely, they can become the reservoirs.