Abnormal overpressure is generally developed in the Huagang and Pinghu Formations of the central overturned structural belt in Xihu Sag

East China Sea Shelf Basin.Oil & gas shows have been reported frequently in these overpressured formations.Formation pressure and pressure profiles of single wells in the formations were calculated and established through Eaton method and based on acoustic well logging

geochemical and testing data

and pressure distribution (both lateral and horizontal) of the area was also defined under the constraint of measured pressure data of the formations.Vertically

the abnormal pressure mainly initiates in the lower member of the Huagang Formation

and increases in stepwise way upwards;and laterally

its top boundary deepens from south to central of the belt.The PetroMod software was employed to simulate the evolution of the formation residual pressure.The results suggest that periods of 13-9 Ma and 4-0 Ma be the key pressure incremental stages.A combination of the above mentioned research with the history of hydrocarbon charging in the area indicates a well match between the times of large scale hydrocarbon charging and pressure increase.A coupling relationship between the abnormal high pressure evolution and hydrocarbon accumulations is finally defined.