准噶尔盆地莫索湾地区异常地层压力与油气聚集

ABNORMAL PRESSURE AND HYDROCARBON ACCUMLATION IN MOSUOWAN AREA OF HINTERLAND OF JUNGGAR BASIN

准噶尔盆地腹部莫索湾地区盆参２井于４５００ｍ和５７００ｍ深处侏罗系内存在异常高压层。根据异常地层压力形成理论、烃类有机成因理论、油气分带模式，探讨了异常地层压力的成因：岩性封闭是先决条件，粘土矿物成岩后生期释放大量层间水，下侏罗统生油层进入低成熟阶段，造成流体增温增压，形成一温跃层，导致异常高压出现。受温压条件控制，勘探目的层侏罗系存在明显的油气分带性：封闭层之上为石油聚集带，之下为凝析油、天然气聚集带。４５００ｍ封闭层以上的侏罗系应是目前勘探的主要对象。

Jurassic abnormally high pressure zones were discovered at a depth 4 500m and5 700 m of Well Pencan 2 inMosuowan area of hinterland of Junggar basin. This paper discusses the origins of abnormal formation pressure,based on the theory on formation of abnormal formation pressure, organic theory and the model of hydrocarbon zona-tion. It is suggested that the lithologic seal is the prerequisite, release of abundant interformational water from clayminerals during katagenesis peried and lower maturation phase of Lower Jurassic source bed resulted in increase influid temperature and pressure, and then abnormally hihg pressure as well as a temperature-active zone were estab-lish. Controlled by the temporature and pressure conditions, oil/gas zonation conspicuously occurs in exploration tar-get zone (Jurassic): oil accumulation zone and condensate or natural gas accumulation zone exist above and beneaththe seal, respectively. Finally, it is concluded that the Jurassic underlain by the seal at 4 500m should be consideredto be main candidate for exploration.