A classification of petroleum accumulation systems (PAS) of marine carbonate fields was attempted by using the latest data of 199 medium to large marine carbonate fields from 53 petroliferous basins around the world and a “source-element” classification scheme.The result shows that PAS of the fields can be categorized into six types: one source-one element

one source-two elements

one source-three elements

two sources-two elements

two sources-three elements and three sources-three elements.The distribution patterns and characteristics of petroleum reserves for each of the 6 types of PAS were investigated and the dominate types with high hydrocarbon richness in marine carbonate petroliferous basins were identified

and their controls on hydrocarbon enrichment were revealed.Statistical analytical results show that one source-three elements PAS not only hosts the largest share of petroleum reserves but also occurs the most widely.It is followed by one source -two elements and two sources-three elements PAS.For other types of PAS

both the reserves and the numbers of occurrence are relatively small.One source-two element PAS is the most promising among all the types but it requires more favorable later preserving conditions.One-source-one element PAS presents itself mostly as unconventional reservoirs but is rarely found in marine carbonate rocks.