Characteristics of Neogene gypsum rocks and their influence on formation pressure in the southern margin of Junggar Basin

The complex formation pressure in the southern margin of Junggar basin brings great difficulties to drilling engineering. The research shows that the genetic mechanism of abnormal formation pressure in the southern margin of Junggar basin, especially in Gaoquan area, is closely related to the development of gypsum rocks in addition to mudstone undercompaction and tectonic pressurization. The gypsum rock in this area is characterized by low gamma value relative to the surrounding rock. The development interval of gypsum rock is abnormal high pressure section, the overlying stratum is normal pressure section, and the overlying stratum is super high pressure section. The super high pressure of AnJiHai formation is due to the strong sealing effect of thick gypsum rock of overlying Shawan Formation.