龙门山推覆构造带北段油气田形成条件探讨
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摘要
通过对龙门山北段L55地震测线的重新解释,结合区域地质研究和油气地球化学分析数据,认为龙门山北段推覆构造有三大特点。一是薄层推覆构造体系使构造分为上下两层,上层复杂,下层相对简单,上层活动,下层相对稳定;上层有一定变质,下层不变质;上层破坏,下层保存好。二是上元古界震旦系陡山沱组黑色页岩是本区最古老的生油层,具有强大的生烃能力。三是油气经多次由西向东运移,古老的生油层生成的油气可以在不同时间形成的不同类型的圈闭中聚集成藏并接受改造或破坏,从而形成地表丰富的油气苗、沥青脉和油砂岩,推覆体下盘则可以形成油气藏。因而建议在勘探中抓住下盘,点面结合进行地震工作,同时建议重点勘探枫顺场潜伏构造和天井山—矿山梁构造东南翼的潜伏断裂构造。
Through reinterpreting the seismic line L-55 in the north section of Longmen mountains and in combination with the regional geological research and oil & gas geochemical exploration data, it was considered that the nappe structures in the north section of Longmen mountains have three characters: first, the thin-layer nappe structural system made the structure be divided into a top formation and a bottom formation, the former being complicated, active, some metamorphic and destructive but the latter being relatively simple, relatively stable, nonmetamorphic and well protective; second, the Doushantuo Formation black shales of Sinian, Upper Proterozoic, were the oldest source rocks in the region and they had strong hydrocarbon-generation capacity; and third, by means of oil & gas migration from west to east for many times, the oil and gas generated from the ancient source rocks might be accumulated in various traps formed in different periods to form oil and gas reservoirs, which could be reformed or destroyed then, thus forming many oil and gas seepages, bituminous veins and oil sands on the surface, but the oil and gas reservoirs might be also protected in the lower walls of the nappes. Therefore it is suggested in the paper that the exploration works should be concentrated on the lower walls; the seismic prospecting should be carried out by combining the point with the area; and the Fengshunchang buried structure and the buried faulted structure on the southeast flank of Tianjingshan-kuangshanliang structure should be emphatically explored.
Through reinterpreting the seismic line L-55 in the north section of Longmen mountains and in combination with the regional geological research and oil & gas geochemical exploration data, it was considered that the nappe structures in the north section of Longmen mountains have three characters: first, the thin-layer nappe structural system made the structure be divided into a top formation and a bottom formation, the former being complicated, active, some metamorphic and destructive but the latter being relatively simple, relatively stable, nonmetamorphic and well protective; second, the Doushantuo Formation black shales of Sinian, Upper Proterozoic, were the oldest source rocks in the region and they had strong hydrocarbon-generation capacity; and third, by means of oil & gas migration from west to east for many times, the oil and gas generated from the ancient source rocks might be accumulated in various traps formed in different periods to form oil and gas reservoirs, which could be reformed or destroyed then, thus forming many oil and gas seepages, bituminous veins and oil sands on the surface, but the oil and gas reservoirs might be also protected in the lower walls of the nappes. Therefore it is suggested in the paper that the exploration works should be concentrated on the lower walls; the seismic prospecting should be carried out by combining the point with the area; and the Fengshunchang buried structure and the buried faulted structure on the southeast flank of Tianjingshan-kuangshanliang structure should be emphatically explored.
引文
[1]张光荣等,川西龙门山断褶带枫顺场构造地震概查总结,四川石油管理局地质调查处,2003
1 宋文海,论龙门山北段推覆构造及其油气前景.天然气工业,1989;9(3):2~9
2 曾宪顺,刘开时,邹景文.论龙门山逆冲推覆构造带北段的地质结构及油气前景.天然气工业,1989;9(3):10~16
3 何军,于三公.龙门山推覆体形成机制及其北段含油气性.天然气工业,1989;9(3):16~21
4 谢邦华,王兰生,张鉴等.龙门山北段烃源岩纵向分布及地化特征研究.天然气工业,2003;23(5):21~23
5 罗志立等.龙门山造山带的崛起和四川盆地的形成与演化.四川成都:原成都科技大学出版社,1995
1 宋文海,论龙门山北段推覆构造及其油气前景.天然气工业,1989;9(3):2~9
2 曾宪顺,刘开时,邹景文.论龙门山逆冲推覆构造带北段的地质结构及油气前景.天然气工业,1989;9(3):10~16
3 何军,于三公.龙门山推覆体形成机制及其北段含油气性.天然气工业,1989;9(3):16~21
4 谢邦华,王兰生,张鉴等.龙门山北段烃源岩纵向分布及地化特征研究.天然气工业,2003;23(5):21~23
5 罗志立等.龙门山造山带的崛起和四川盆地的形成与演化.四川成都:原成都科技大学出版社,1995
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