玛湖-盆1井西复合含油气系统低压特征与成因

随着油气勘探的不断深入，已在越来越多的沉积盆地中发现了低压现象，但对低压成因及其与油气运聚分布关系的研究则显得不足。玛湖-盆1井西复合含油气系统是准噶尔盆地油气分布最集中的地质单元，研究表明该系统地层中高压和低压均存在，侏罗系及以上地层中多低压，且在气藏分布区低压更突出，形成较开放性的压力系统。随着盆地的形成演化，异常地层压力亦有产生、发展和消亡的过程。玛湖-盆1井西复合含油气系统中低压的形成与油气运移过程中轻烃组分的漏失量大于油气和地下水的运移补给量，同时盆地抬升剥蚀和地温的持续下降，进而造成地层中能量亏损有关，而低压的形成时间则应该在古近纪。

CHARACTERISTICS AND ORIGIN OF SUBPRESSURE IN MAHU-PENYIJINGXI COMPOSITE PETROLEUM SYSTEM

Subpressure has been discovered in more and more sedimentary basins along with the deepening of exploration. However, their origin and relationships with hydrocarbon migration, accumulation and distribution are poorly understood. The Mahu-Penyijingxi composite petroleum system is a geologic unit with the most abundant hydrocarbon distribution in the Junggar Basin. Both surpressure and subpressure exist in this petroleum system, and subpressure mainly occurs in Jurassic and the a-bove strata, especially in areas with gas reservoirs and an open pressure system. Along with the basin evolution, abnormal formation pressure also goes through a process of generation, development and disappearance. The subpressure of the petroleum system might be caused by the following factors: the volume of light hydrocarbon leaked in the process of hydrocarbon migration was larger than the volume of hydrocarbons and groundwater recharged, the basin was uplifted and eroded, the formation temperature declined continuously, and the formation energy depleted. The subpressure might occur in Paleogene.