焉耆盆地含油气系统分析

焉耆盆地中生界含油气系统中,八道湾组是最主要的烃源岩层,烃源岩类型主要为煤系泥岩。三工河组是主要的储集层,储层砂体类型为辫状河三角洲和扇三角洲,储集条件较差,属低孔低渗型。古圈闭于J1s期开始形成,发育侏罗纪末期、第三纪末至今两次生排烃事件。油气以沿断层垂向运移为主。对应于两次成藏事件,划分出原生和再生两个含油气子系统。含油气系统演化经历了三个阶段:①侏罗纪末期古油气藏的形成;②燕山中、晚期构造运动与古油气藏的调整、破坏;③第三系的覆盖和喜山期现今油气藏的形成。断层的多期活动性和燕山中晚期的抬升剥蚀作用改造、破坏了早期形成的油气藏,喜山期定型的油气藏现今保存完好。

An Analysis on Petroleum System in Yanqi Basin

In the Mesozoic petroleum system in Yanqi basin,the Badaowan Formation is the principle source rock with coal-measure mudstone as the main type of source rock.The Sangonghe Formation is the main reservoir with braid ed river and fan delta as the key sandboy types.Reservoir conditions are poor and it belongs to low porosity and low permeability reservoir types.The paleo-traps took shape in J 1s .Two hydrocarbon generation and expulsion events occurred,one at the end of Jurassic and the other from the end of Tertiary till now.Most of the hydrocarbon migrated vertically along the faults.Two petroleum systems,one primary and one secondary,are recognized corresponding to two reservoir-forming events.The evolution of petroleum system went through3stages:formation of paleo-traps at the end of Jurassic;tectonic movement and modification and destruction of plaeo-reservoirs during the middle and late stages of Yanshan period;and overlying of the Tertiary and formation of the current reservoirs in Himalayan period.The reservoirs formed at early stages were destructed by the multistage activation of faults and by uplift and erosion occurred during the middle and late stages of Yanshan period,while the reservoirs formed during Himalayan period are well preserved till present.