川西坳陷中部上三叠统烃源岩动态演化模拟

Dynamic evolution simulation of the Upper Triassic source rocks in central part of western Sichuan Depression

江兴歌 曾华盛 朱建辉 曹倩

Jiang Xingge Zeng Huasheng Zhu Jianhui Cao Qian

川西坳陷中部上三叠统烃源岩在须家河组三段沉积时期开始成熟,早侏罗世晚期进入高成熟阶段,晚侏罗世达到过成熟阶段。川西坳陷西深东浅的构造格局,导致烃源岩演化具有西早东晚、西高东低的特点。须家河组三段沉积末期,成熟度相对较高的地区靠近龙门山前;至须家河组五段沉积末,成熟度相对高的地区向东扩展,最高点向北迁至龙深1井附近。侏罗纪末,成熟度相对较高的地区整体向东迁移。白垩系末到现今,形成以绵阳、德阳、彭州和大邑一线为核心的高演化区,以马深1井和大邑北为最高点。川西坳陷中部须家河组烃源岩总生气量为1 678 125×10 m。其中,马鞍塘组-须家河组三段沉积时期生气量仅占总生气量的2.53%,须家河组四段至五段沉积时期占10.84%,早、中侏罗世占22.79%,晚侏罗世占22.87%,白垩纪占40.97%。

The Upper Triassic source rocks in the central of western Sichuan Depression got mature during the deposition of the 3 member of Xujiahe Formation,over-mature stag in the late of Early Jurassic and post-mature in the Late Jurassic.The EW-dipping tectonic framework in western Sichuan depression determines that the source rocks in the west got mature earlier and have higher maturity than that in the east.Area with high maturity was near the piedmont of Longmen Mountain at the end of deposition of the 3 member of Xujiahe Formation,and it extended eastwards with the highest maturity migrating near to Longshen-1 well at the end of deposition of the 5 member of Xujiahe Formation.Later it migrated eastwards as a whole at the end of the Jurassic.The area with high maturity has centered in Mianyang-Deyang-Pengzhou-Dayu from the Creataceous to present,with the highest maturity occurring at Mashen-1 well and Dayu North.The whole amount of gas generated from source rocks in the Xujiahe Formation in western Sichuan depression is 167.812 5 tcm.The gas generated during the deposition of the Maantang Formation-3 member of Xujiahe Formation accounts for 2.53% of the total,that during the deposition of 4 and 5 members of Xujiahe Formation accounts for 10.84%,that in the Early and Middle Jurassic 22.97%,that in the Later Jurassic 22.86% and that in the Early Cretaceous 40.97%.

10.11743/ogg20120408