陆相断陷湖盆生烃潜力的古气候波动响应研究——以东濮凹陷古近系文古4井为例

古气候波动会影响古沉积环境,从而造成沉积物组分的变化,并最终导致沉积岩生烃潜力的变化。陆相断陷湖盆是我国陆相含油气盆地的重要类型,近年来还成为重要的致密油藏勘探区,但关于气候波动对地层生烃潜力影响方面的研究还较为匮乏。东濮凹陷是在中-古生界基底上发育起来的一个新生代断陷咸化湖盆,在构造稳定期其沉积记录主要受短期气候波动影响。本文以东濮凹陷古近系文古4井为例,综合运用矿物学、微体古生物学和有机地球化学方法来揭示古气候波动与生烃潜力之间的成因联系。结果显示,古近系沙河街组(沙三上8～10段)形成于整体较为干热的气候背景中,期间发生多次短周期的相对干旱-潮湿波动,古气候波动不仅体现在孢粉化石和岩石的矿物组成上,而且影响了有机碳的含量,使其随着气候的相对干旱-潮湿波动发生减少-增加的变化。本次研究结果提示构造稳定期内短周期的气候波动是影响陆相断陷湖盆生烃潜力的重要因素,相对潮湿的气候更有利于有机质的富集。

Paleoclimate response of hydrocarbon generation potential for the lacustrine rift basin:A Paleogene example from Wengu 4 well in Dongpu Depression

Paleoclimate fluctuations directly or indirectly change ecosystem,and sediment composition,which leaded to that the change of hydrocarbon generation potential of sedimentary rocks.Lacustrine rift basin,one important type of petroliferous basin,has currently been recognized to be an important tight oil exploration area.However,study on co-variation between climate fluctuation and hydrocarbon generation potential is absent.Dongpu Depression,developed on Paleozoic-Mesozoic basement,is a Cenozoic lacustrine rift basin,whose sedimentary records were mainly controlled by short-term climate fluctuations during tectonic quiescent period.In this study,compilation and comparison of mineralogy,micropaleontology and organic geochemistry data from Wengu 4 well in Dongpu Depression were used to reveal the genetic relationship between paleoclimate fluctuations and hydrocarbon generation potential.The results suggest that the Paleogene Shahejie Formation(third member 8~10)was formed in overall dry-hot climate,with several times of climate fluctuations between relatively dry and relatively humid,which correspond to the waning and waxing of organic content.Co-variation of climate and organic content from Shahejie Formation indicate a genetic relationship between paleoclimate fluctuations and hydrocarbon generation potential,humid climate is more beneficial for the accumulation of organic matter.