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龙门山前陆盆地上三叠统为一厚度巨大的陆相含煤碎屑岩系,其沉积厚度最大达3000m以上;它是前陆盆地内唯一具生烃潜力的烃源岩层,以腐殖型干酪根为主。上三叠统的镜质体反射率在0.5％～2.5％之间,有机质成熟度从上向下由成熟阶段→高成熟阶段→过成熟阶段而逐渐增高。因上三叠统下部岩层在晚侏罗世进入成熟阶段,推测其油气二次运移开始于晚侏罗世末的构造运动。但龙门山前陆盆地与其它含油气沉积盆地不同的是:上三叠统油气未发生大规模的二次侧向运移,只有经早第三纪末的构造活动后,才出现了明显的二次垂向运移。这种油气二次运移特点,造成前陆盆地内油气成藏有三种类型:侏罗系红层中的次生气藏;现坳陷区上三叠统成岩圈闭气藏;侏罗纪古坳陷区上三叠统背斜圈闭气藏。
The Upper Triassic of the Longmen Shan foreland basin is a continental monolithic clastic rock with a maximum thickness of more than 3000 m. It is the only source rock with hydrocarbon potential in the foreland basin, Kerogen based. The vitrinite reflectance of the upper Triassic ranges from 0.5% to 2.5%. The maturity of organic matter increases from the mature stage → the high mature stage → the mature stage from the top to the bottom. Due to the late Upper Triassic strata entering the maturity stage in the Late Jurassic, it is speculated that the secondary migration of oil and gas began in Late Jurassic tectonic movement. However, the difference between the Longmenshan foreland basin and other petroliferous sedimentary basins is that no large-scale secondary lateral migration of the Upper Triassic oil and gas occurred. Only after the tectonic activity of the end of the Tertiary Period had obvious Secondary vertical migration. The secondary migration of oil and gas causes three types of hydrocarbon accumulation in the foreland basin: secondary gas reservoirs in the Jurassic red beds, gas reservoirs in the upper Triassic diagenetic zone in the depression area, Jurassic paleosols Trapped Upper Triassic anticline trap gas reservoirs.