从四川盆地看古隆起成藏的两重性

The pros and cons of paleohighs for hydrocarbon reservoiring:A case study of the Sichuan basin

从四川盆地乐山—龙女寺加里东期、泸州—开江印支期两大隆起在油气成藏中的作用入手,类比论证了不同性质的古隆起对油气藏形成的利与弊。结果表明:①泸州—开江印支期隆起属继承性沉积型隆起,剥蚀幅度弱,中石炭统黄龙组"天窗"展布范围小,而且发生在下志留统油系烃源大量排烃之前,有利于古油藏、古气藏的形成与保藏,该区勘探程度虽已较高,但仍具勘探前景;②乐山—龙女寺加里东隆起,属剥蚀型隆起,剥蚀幅度大,延续时间长,震旦系灯影组"天窗"发生在古气藏形成之后,古气藏遭受明显破坏,导致现今气藏气源不足,该区勘探宜转向古隆起外围,目的层以下古生界为主。结论认为:印支期隆起有利于油气的富集与储存,应列为勘探的主要靶区。

Through comparison analysis on the roles of two paleohighs in hydrocarbon reservoiring in the Sichuan basin,one is in the Caledonian movement in the Longnushi of Leshan,another one is in the Indo-Chinese epoch in the Kaijiang of Luzhou,and this study demonstrates that there are pros and cons of different kinds of paleohighs on the hydrocarbon accumulation.The paleohigh in the Indo-Chinese epoch in the Kaijiang of Luzhou belongs to sedimentary succession of uplift with a low rate of denudation,so-called 'skylight'.The 'skylight' in the Huanglong formation of Middle Carboniferous Series with a small range of distribution came into being before amounts of oil expulsion in hydrocarbon source beds,and this provides a good condition for the forming and sealing of palaeo hydrocarbon reservoirs.There is still high potential for hydrocarbon exploration in this favorable zone.Another paleohigh in the Caledonian movement in the Longnushi of Leshan is a kind of denudation of uplift with a high rate of denudation and a long period of extending time.The 'skylight' in the Dengying formation of the Sinian system occurred after the formation of palaeo hydrocarbon reservoirs,which was destroyed significantly.So there are no enough gas sources from the present gas reservoirs and the exploration has to turn to the periphery of this paleohigh for the main target zone of the Lower Paleozoic.This paper concludes that the Indo-Chinese epoch paleohigh is favorable for hydrocarbon reservoiring and will be the main target zone for oil and gas exploration.