Overpressure is common in the Jurassic formation of the central part of Junggar Basin. Overpressure layer has a better response relationship with interval transit time and resistivity, especially the resistivity response, which is characterized by abnormal high value of interval transit time and low resistivity of resistivity. In this paper, large numbers of well-logging, tests and geological data in the central part of Junggar Basin are used to determine the origin of overpressure. The author puts forward that the overpressure developed in the mudstone and sandstone is not caused by compaction and structural extrusion, but mainly by the effect of hydrocarbon generation. The result shows that there are several main evidences: 1）The overpressure mudstone density does not have abnormal low characteristic; 2）There is no linear relationship between the density of overpressure segment and the vertical effective stress of rock particles; 3）There is no abnormal high ground temperature gradient phenomenon in overpressure sandstone; 4）The depths to the top of the overpressure range from 3 800 m to 4 300 m and the temperature for the top of overpressure zones is approximately 90 ℃～125 ℃, corresponding to an estimated vitrinite（Ro%）of 0.6%～0.9%; 5）The Jurassic hydrocarbon source rocks in the overpressure layer can reach up to 70% at present, and the average oil rate can reach 90 mg/g·TOC, and they still have strong hydrocarbon generation ability; 6）The clay source rock itself has a good sealing effect on overpressure; 7）There is a large number of low angle or high angle microfractures developed in Jurassic hydrocarbon source rocks; 8）The overpressure reservoir is mainly based on oil layer, without water layer. It concluded that the overpressure of sandstone is mainly the result of overpressure transmission from the overpressure source rock in Dongdao Haizibei depression of Junggar Basin.
Yu Chunyong Ren Zhanli Guo Xiaowen Chen Zhipeng Ren Wenbo Yang Guilin Ma Qian Yang Yan Liu Runchun. The mechanism of overpressure within the Jurassic formation in the central part of Junggar Basin: Dongdao Haizibei depression[J]. Chinese Journal of Geology, 2018, 53(3): 893-907.