四川盆地乐山-龙女寺古隆起震旦系天然气成藏史

应用天然气生成和同位素分馏的化学动力学方法对四川盆地乐山-龙女寺古隆起震旦系天然气成藏史进行研究。结果表明：①高石梯-磨溪含气构造为继承性隆起，有利于天然气的高效聚集，震旦系灯影组主要聚集191 Ma以来所生天然气，早期所生天然气未运聚成藏或散失，成藏参与率约为79%；②资阳构造圈闭受燕山期构造运动影响逐渐演化成威远构造的斜坡，构造运动调整过程中剩余未裂解原油运移至新的构造高部位——威远构造继续裂解，资阳和威远气田分别聚集构造调整前后（106～104 Ma）所生天然气；③威远气田构造圈闭由于形成较晚，捕捉到的原油裂解气有限，成藏参与率约为51%，低于高石梯-磨溪地区；④资阳-威远地区构造反转过程中资阳古隆起中天然气会大量散失，尽管高石梯-磨溪地区天然气生成结束的时间早于资阳-威远地区90 Ma，不利于保存，但其气藏充满度却高于资阳-威远地区。

History of natural gas accumulation in Leshan-Longnyusi Sinian paleo-uplift,Sichuan Basin

History of natural gas accumulation in Leshan-Longnyusi Sinian paleo-uplift in the Sichuan Basin was studied with chemical kinetic methods of gas generation and isotopic fractionation.The results show that:①Gaoshiti-Moxi gas bearing structure is an inherited uplift which is conducive to efficient accumulation of natural gas.The natural gas generated since 191 Ma mainly gathered in the Sinian Dengying Formation,while that generated earlier didn't accumulate or dissipated after accumulation.The gas accumulation participation rate is about 79%.②The Ziyang structural trap gradually evolved into a tectonic slope of Weiyuan trap during the Yanshan tectonic movement.The remaining non-pyrolysed crude oil migrated to the new structural high-Weiyuan trap and continued to pyrolyse there during the tectonic movement.So Ziyang and Weiyuan gas fields gather the natural gas generated before and after structural adjustment(106-104 Ma),respectively.③Weiyuan structural trap captured limited pyrolysis gas due to its late formation,and its gas accumulation participation rate is about 51%,which is lower than that in Gaoshiti-Moxi area.④Much natural gas in Ziyang paleo-uplift was lost during Ziyang-Weiyuan tectonic inversion.Although the ending of gas generation in Gaoshiti-Moxi area is 90 Ma earlier than that in Ziyang-Weiyuan area,which is not conducive to the preservation,its gas reservoir fullness is higher than the later area.