Characteristics of hydrocarbon generation and expulsion in matrix and stylolite of carbonate rocks

Characteristics of organic matter content, hydrocarbon generation and expul sion of carbonate rocks are discussed by analysis of organic carbon and pyr olysis. There is a strong inhomogeneity in distribution of organic matter i n carbonate rocks. The organic matter abundance is higher in stylolites, ca rbonate varves or marls, while it is the lowest in matrixes (purer carbonat e rocks around stylolites). Because of stable thickness and broad area, mar ls and carbonate varves may become good source rocks. At the same depth, st ylolites, carbonate varves and matrixes generate and expel hydrocarbons alm ost at the same time. Expulsion efficiency of carbonate varve is the highes t; that of matrixes is the lowest and that of stylolites is between marl's or carbonate varve's and matrix's.