准噶尔盆地南缘新近系膏质岩特征分析及其对地层压力影响研究

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

准噶尔盆地南缘复杂的地层压力给钻井工程带来极大困难。研究表明,准噶尔盆地南缘尤其高泉地区,地层异常高压的成因机制除了泥岩欠压实作用和构造增压作用之外,与膏质岩发育情况密切相关。该区膏质岩相对围岩以低伽马值为显著特征,膏质岩发育层段为异常高压段,上覆地层为常压段,下覆地层为超强高压段。安集海组超强高压得益于上覆沙湾组厚层膏质岩的强力封闭作用。

The complex formation pressure in the southern margin of Junggar Basin brings great difficulties to drilling engineering.The research show 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 under compaction 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.