准噶尔盆地超压系统分布及其演化

钻井揭示准噶尔盆地超压明显,且不同地区超压出现的深度和层位不同。本文将准噶尔盆地在纵向上划分为上部、中部和下部3套超压系统。上部超压系统顶界受古近系安集海河组控制,底界受下白垩统胜金口组控制,构成压力封存箱。中部超压系统的封隔层为三工河组,构成顶封滞排型异常压力系统。下部超压系统发育在三叠系及以下地层之中,以白碱滩组为封隔层构成顶封滞排型异常压力系统。三者在平面上有不同的分布范围。白垩纪是准噶尔盆地超压形成的开始期,新近纪得到进一步加强。其中,下部超压系统开始形成于白垩纪早期,中部超压系统开始形成于白垩纪中期,而上部超压系统形成的最早时期应为中新世。

DISTRIBUTION AND EVOLUTION OF OVERPRESSURE SYSTEMS IN THE JUNGGAR BASIN

The drilling practice revealed that there was apparent overpressure in the Junggar Basin, which was unevenly distributed corresponding to different depth and formation. The overpressure systems were categorized vertically into three types:the upper, middle and lower overpressure systems. The top and the bottom parts of the upper overpressure system was controlled by the Paleogene Anjihaihe Formation and the Cretaceous Shengjinkou Formation respectively, both of which constructed the pressure sealing box. The sealing bed of the middle overpressure system was the Jurassic Sangonghe Formation, and constructed the overpressure system characterized by top sealing and stagnancy. The lower overpressure system was mainly developed in the Triassic and even lower strata, and sealed by the Triassic Baijiantan Formation to construct the overpressure system characterized by top sealing and stagnancy. Transversely, the three systems covered varied regions: the upper one only limited in the southern marginal part of the basin, and the lower one covered almost the whole basin. The overpressure originated in the Cretaceous and was strengthened in the Neogene. Among which, the lower overpressure system was formed in the Early Cretaceous, the middle one formed in the Middle Cretaceous, whereas the upper one originated in the Miocene.