琼东南盆地乐东凹陷烃源岩热史及成熟史模拟

Geothermal and Maturation Histories Modeling of the Source Rocks in the Ledong Sag,Qiongdongnan Basin

琼东南盆地乐东凹陷烃源岩热史及成熟史研究对乐东凹陷油气资源评价及勘探选区具有指导意义。在盆地地史和热史恢复的基础上,利用EASY%Ro模型模拟重建了琼东南盆地乐东凹陷崖城组烃源岩的成熟史。研究结果表明,琼东南盆地具有较高的古、今地温梯度,且古地温梯度多高于现今地温梯度,有利于烃源岩的成熟与天然气的生成。始新世-早渐新世断陷期和晚中新世-第四纪加速沉降期的热流值高,晚渐新世断坳期和早-中中新世坳陷期的热流值相对较低。乐东凹陷主力烃源岩崖城组的热演化程度高,整体已进入生烃高峰期,可为凹陷油气聚集提供大量的烃类来源;凹陷西北部崖城组烃源岩的热演化程度高于东南部,具有广阔的天然气勘探前景。

The study of the geothermal and maturation histories of the source rocks in the Ledong Sag,Qiongdongnan Basin is significant for the hydrocarbon evaluation and decision for exploration areas.Based on geohistory and geothermal history in the sag,the source rock maturation history of the sag is reconstructed by Easy% Ro model.It is indicated that Qiongdongnan Basin has a higher paleo and present geothermal gradient,while the paleogeothermal gradient is higher than the present geothermal which it is of great help for the maturity of the source rocks and the generation of gas.The heat flows of the fault period（from Eocene to Early Oligocene） and the accelerated subsidence stage（from Late Miocene to Quaternary） are higher while that of the fault-depression period（Late Oligocene） and the depression period（Early Miocene to Middle Miocene） is relatively lower.The thermal evolution of main source rocks of Yacheng Formation in the Ledong Sag is higher,showing it has entered the hydrocarbon generation peak.This can provide vast hydrocarbon sources for the oil and gas accumulation in the sag.The thermal evolution of source rocks of the Yacheng Formation in the northwest is higher than that in the southeast with a great gas exploration prospect.