Three sets of gypsolyte-salt rocks occur vertically in Es

4

(the fourth member of the Shahejie Formation) of the Dongying Sag

the Bohai Bay Basin.The gypsolyte-salt rhythmic units show apparent depositional sequence of evaporation in genesis.On plane view

the gypsolyte-salt rocks are in ring-like distribution

and salt rock

gypsolyte

argillaceous gypsolyte

carbonate

marl

and clastic rock occur successively from the center to the border of the basin.Studies based on formation pressure coefficient calculation through interval transit times and statistics of the measured pressures show that the Paleogene presents vertically a "double layer structure" with normal pressure at the upper part and abnormal high pressure at the lower part.On plane view

the distribution of the abnormal pressure matches well with that of the gypsolyt-salt-rocks.It is suggested that the gypsolyte-salt-double seal mechanism of pressure seal and physical property seal is one of the key elements controlling the formation of the abnormal pressure in Es

4

in Dongying depression.