The lower 2

nd

member and 3

rd

member of the Dongying Formation

the 1

st

and 3

rd

member of the Shahejie Formation are four source rocks in Liaozhong Sag.The latter three are active source rocks

but the lower 2

nd

member of the Dongying Formation is immature to lowly mature.The 3

rd

member of the Shahejie Formation in the northern subsag of the Liaozhong Sag is the main source rocks for the JZ20-A oilfield.The source rocks in the 3

rd

member of the Shahejie Formation are of high organic content and maturity

thus have great potential for hydrocarbon generation.By analyzing the inclusion of the major pay zones in the well JZ20-A

we performed the timing of the hydrocarbon generation and established the hydrocarbon accumulation model in the JZ20-A oilfield.The results indicate that the homogenization temperature of the inclusion is 120-140 ℃. The hydrocarbon charging mainly occurred at 5 Ma ago when the Minghuazhen Formtion was deposited.Hydrocarbon charging also happened at 27 Ma ago when the Dongying Formation deposited.All the reservoirs of JZ20-A oilfield are high in hydrocarbon abundance.The GOI value of the inclusion is above 5%.The characteristics of the hydrocarbon accumulation are relay-type multiple stage hydrocarbon charging

over-pressured shale sealing on both sides and oil/gas accumulation in superimposed multiple layers.