Characteristics and Genetic Mechanism of the Pressure Field of the Damintun Depression
大民屯凹陷压力场特征及其成因机制探讨

Abnormal geopressure widely existent in the sedimentary basin is of great significance in the study of hydrocarbon generation and accumulation. There are four types of shale compaction, namely, strong undercompaction, undercompaction, local undercompaction and normal compaction. With the equivalent depth method, the authors calculated the overpressure along five profiles with sonic log data and discussed its origin. The results show that overpressure is widely distributed in damintun depression. Vertically, there exist three geopressure systems, i.e., the normal geopressure system within and above Es3_2, the weak overpressure system in Es3_3 and the overpressure system in Es4_3 and Es_4. Horizontally, overpressure is strong in the center of the sag and turns into normal pressure on the slope. Unbalance compaction and hydrocarbon generation constitute the main mechanism of overpressure.