渤南洼陷盐湖-咸水湖沉积组合及其油气聚集

济阳坳陷下第三系沙河街组沉积早期,一些凹陷的蒸发岩系中发育了大套暗色泥岩。一般认为蒸发岩的形成环境不利于烃源岩的沉积,因此对这种烃源岩的生烃潜力一直未给予足够的重视。通过对沾化凹陷沙四段上部厚逾500m的蒸发岩沉积组合及其成因研究,认为湖相蒸发岩不但可以和烃源岩共生,而且可以和优质烃源岩共生。在盐湖或咸水湖条件下,湖泊表层与底层水的盐度差可以导致盐跃层的形成,上下水层受到分割导致湖盐度的长期性分层。底层水循环作用处于完全停滞的封闭状态,形成缺氧环境,抑制了底栖生物的活动性,使得沉积有机质得到最大限度的保存。油源对比表明,盐湖-咸水湖相烃源岩是渤南洼陷重要的烃源岩,控制了洼陷许多种油气藏的形成和分布。

SALT LAKE-SALINE LAKE SEDIMENTARY COMBINATION AND PETROLEUM ACCUMULATION IN THE BONAN SAG

On the early age of Paleogene Shahejie Formation, large set of dark mudstones develop in theevaporite in some depressions. In a general way, people think evaporite-generation environment isn't benefit for source rock sedimentation, So enough attention isn't paged to its hydrocarbon-generation potential for this source lock. By researching the evaporite sediment combination up to 500 m on the upper Sha 4 in Zhanhua depression and its origin, the author think lake facies evaporite exists not only with source rock, but also with high quality one. In salt lake on saline lake, the salinity difference between surface and bottom layers could resultin the salt transition layer and the division of upper and lower layers makes a long-rang delamination of salinity. Bottom water circulation is in a absolutely stagnant state and results in anoxia environment. This environment restrains the activity of benthon and makes a maximum presevation of sediment organic matters. Oil-source correlation shows that salt lake-saline lake source rock is an important one in Bo Nan Sag and controls the formation and distributionof many pools.