A method for calculating the quantity of hydrocarbon generation and expulsion

Hydrocarbon generating quantity of source rock is the sum of hydrocarbon remaining quantity in the source rock and hydrocarbon expelling quantity from the source rock. Hydrocarbon retention rate in the source rock can be obtained by analyzing the ratio of the extracts A over TOC. The decrease of ( S 1+ S 2)/TOC, which is the hydrocarbon generation potentials, during the evolution of source rock indicates that parts of the hydrocarbons generated by the source rock have been expelled from the source rock. No matter what the hydrocarbon generation mechanism of the source rock is, the difference between the current hydrocarbon generation potential index of source rock and the original hydrocarbon generation potential index before the hydrocarbon expelling from source rock always stands for current hydrocarbon expelling quantity of a unit weight of organic carbon (i.e. hydrocarbon expelling rate), based on this, it is able to calculate the hydrocarbon expelling quantity from source rocks in which unmatured low matured oil were generated. The hydrocarbon generation quantity of the source rock can be calculated through extracting hydrocarbon generating rate of source rocks and combining with the data about the source rock, such as thickness, area, TOC, vitrinite reflectance, kerogen type and density obtained. Application results of the method in Bamianhe oil field in Dongying depression indicate that the hydrocarbon generation and expulsion evolutionary patterns of mudstones and shales of Members S 3 and S 4 in Lower Tertiary of this area are different, the hydrocarbon generating quantity of mudstones is much larger, but its hydrocarbon expulsion efficiency is lower than that of shale.