Abstract:

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.

Key words: uncompaction, pressure sealing, formation pressure anomaly, lateral and vertical prediction