CHARACTERISTICS OF THE ABNORMAL PRESSURE SYSTEM IN THE LISHUI SAG OF THE DONGHAI BASIN

The Tertiary rapid-deposited strata were developed in the Lishui Sag.Very obvious abnormal pressure is an important feature of them. By using geologic,drilling,logging and testing information in this paper,the types,genetic mechanism and distribution of abnormal pressure are studied based on the analysis of abnormal pressure in main test wellls. The study reveals that the abnormal pressure in the Lishui Sag belongs to the top-sealed expulsion-retarded abnormal pressure system,the pressure gradient of overpressure belts is obviously different,and the overpressure belts can be divided into the sealing layer overpressure belt,the pressure transitional belt and the ultrahigh pressure belt three abnormal pressure belts longitudinally.