The measured pressure data and pressures calculated with balanced depth method are used to reconstruct pressure profiles and classify vertical pressure variation sequences in single well in Zhanhua sag.Two different types of sub-sag

i.e. sub-sags with normal-transitional and transitional-abnormal pressure

are recognized in the Paleogene Shahejie Formation in the sag where the vertical superimposed pressure field controls the distribution of oil and gas pools.There are three modes of coupling relationships between the reservoirs in the 4th member of Shahejie Formation(Es

4

) and the pressure fields: abnormal-pressure reservoirs

transitional-pressure reservoir

and normal-pressure reservoirs

among which the mode that oil with double lithologic and pressure seal are the most favorable to the formation of high yield reservoirs.The middle-deep normal pressure zone and transitional pressure zone in sub-sag of transitional-abnormal pressure are potential plays for the disco-very of high yield oil layers in the Es

4

.