龙门山北段天井山构造演化及其对油气聚集的控制

Formation evolution and control of hydrocarbon accumulation in north part of Tianjing mountain in Longmen ranges

龙门山褶皱冲断带位于四川克拉通以东,被围限在扬子、华北和羌塘三大陆块拼贴构造间.以全工区地震精细解释为基础,结合野外调查,选取近东西向的剖面06fsc0003—02tjs1111线,利用平衡剖面法恢复天井山构造带的造山过程.结果表明:天井山构造带的演化可划分为伸展拉张成盆阶段(震旦纪—中三叠世末)、陆隆伸展演化阶段(晚三叠世—中侏罗世末)、挤压抬升剥蚀阶段(晚侏罗世—现今)3期.根据生储盖组合和油气运移条件,认为自元古代以来最大主应力性质发生多次改变,控制构造变形、生储盖组合分布及厚度、断裂特征和油气运聚.印支期冲断带下盘(现今天井山背斜前翼下部)发育形成于印支期晚期的冲起构造,其内断层发育,将二叠系、志留系及寒武系烃源岩与二叠系储层和圈闭串通,有利于烃类的运聚,且有飞仙关组泥岩作为直接盖层,保存条件较好,是油气集聚的有利部位.该研究能够加深对龙门山褶皱冲断带油气分布预测的认识,对油气勘探具有指导意义.

Interpretation of the whole work area seismologic,combined with well drilling and field survey,we selected east-west profile of line 06fsc0003—02tjs1111.The evolution of Tianjing Mountain region can be regarded as being divided into four stages:stretching basin-formation(Sinian-Terminal Middle Triassic),continental emergence stretching evolution stage(Late Triassic-Terminal Middle Jurassic),lifting and denudation stage(Late Jurassic-Terminal Early Cretaceous) and reformation succession stage(LateCretaceous-Present).The conditions about the migration of oil and gas and the combinations of source rock,reservoir and cap rock are analyzed.The faults are believed to be developed which existed in the heading side which was formed in the later period of Indonesia epoch.Due to the existence of faults,the oil trapsand resource rock is connected,which is advantageous to the migration of oil and gas.Since the mudstone of Feixianguan formation is direct the cap rock,the condition of oil preservation is good,which makes the profitable areas obvious.