北部湾盆地海中凹陷古近纪古气候研究

古气候对烃源岩的发育具有重要的控制作用,温暖湿润的气候成为优质湖相烃源岩发育的有利气候条件。本次根据X1井及X2井的孢粉资料及粘土矿物数据,采用孢粉定量统计分析与粘土矿物分析相结合的方法,对海中凹陷中始新世—晚渐新世的古气候进行了研究。研究显示海中凹陷流沙港组二段沉积时期(中—晚始新世)气候相对温暖湿润,为南亚热带湿润—半湿润气候;流沙港组一段沉积时期(晚始新世—早渐新世早期)气候开始转凉,为中亚热带湿润—半湿润气候;涠洲组沉积时期(早渐新世晚期—晚渐新世晚期)气候逐渐变得干燥,为中亚热带半湿润—半干旱气候,同时明确了流沙港组二段沉积时期为海中凹陷优质湖相烃源岩发育的最佳时期。

THE STUDY OF PALEOGENE CLIMATE IN THE HAIZHONG DEPRESSION,BEIBUWAN BASIN,NORTHERN SOUTH CHINA SEA

Palaeoclimate has an important role in the control of hydrocarbon source.The warm and humid climate condition is favorable for the development of high quality lacustrine hydrocarbon-source rocks.Based on the quantitative sporopollen analysis and clay minerals analysis,in the wells of X1and X2of the Haizhong depression,Beibuwan Basin,northern South China Sea,this paper studies the palaeoclimate during the middle Eocene to the late Oligocene.The results have shown that during the depositional period of E2 l 2(middle—late Eocene)the climate was relative warm and humid(a southern subtropical humid to semi-humid climate condition);during the depositional period of E2 l 1(late Eocene—early stage of Early Oligocene)the climate began to become cool(a middle subtropical humid to semi-humid climate condition);and during the depositional period of E3 w(late stage of Early Oligocene—Late Oligocene)the climate gradually become dry(a middle subtropical semi-humid to semi-arid climate condition).The depositional period of E2 l 2 was suggested to be the best period to develop high quality lacustrine hydrocarbon-source rocks in the Haizhong depression.