The sealing capability of cap rocks is closely related to the porosity

permeability

the ratio of sand to mud contents and fluid pressure of the rocks.The sealing capability could be predicted by using seismic interval velotity and acoustic time.At first

fitted experiment formula is used to calculate some physical parameters such as porosity and residual fluid pressure

then calculate formation pressure

and finally predict and evaluate the sealing capabilities both laterally and vertically according to the calculated results.As compared with actual measured results

the absolute errors of the predicted porosity of seal rocks are -1.32%～-1.39%

their proportional errors are 3.07%～15.4%;and that the absolute errors of break out pressure are -0.23～0.63 MPa

their proportional error are 1.81%～12.27%.The results show that the abnormal formation pressune system resulted from uncompaction has obviously controlled the migration

accummulation

preservation and distribution of hydrocarbon.