龙门山系山前带北段超晚期断褶构造与油气远景

龙门山系属上扬子地台内晚中新生代断褶构造活动形成的山系。川西断陷区属龙门山系的前陆盆地,是地台型海相沉积与前陆型陆相沉积组成的复合型含油气区。超晚期(N-Q)断褶构造的发育程度控制了龙门山系山前带构造圈闭的发育和裂缝型气藏的形成。印支晚期形成的天井山古隆起因受强烈的超晚期断褶构造活动的影响,使原有的油气藏遭到破坏。天井山古隆起北东倾伏端的广元昭化地区,发育隐伏断裂系伴生的背斜群,是较理想的油气聚集带;而天井山古隆起西南倾伏端的绵阳-江油-安县地区,为北东向及北西向深断裂交叉复合区,是寻找中、浅层次生气藏的有利地区。

THE LATEST FAULT-FOLD STRUCTURE AND PETROLEUM PROSPECT IN THE NORTHERN FOOTHILL BELT OF LONGMEN MOUNTAIN SYSTEM

The formation of Longmen mountain system is duo to the faulting-folding on the Upper Yangtz platform in late Mesozoic-Cenozoic. The western Sichuan fault-depression belongingb to the foreland basin of Longmen mountain system is a composite oil-gas province that consists of platform-type marine sediment and foreland-type continental deposit. The maturity of latest (NQ) fault-fold structure controls the development of structural traps in the foothill belt and the formation of fissured gas pools. Oil and gas accumulations on the Tianjingshan paleo-uplift formed in late Indosinian were destroyed as a result of intensive activities of the latest faulting-folding. Zhaohua area in Guangyuan county, at the NE pinching end of Tianjingshan paleo-uplift, is a favorable oil-gas accumulation belt because there developed a buried fault system and its accompanying fold group. And MianyangJiangyouAnxian area, at the SW pinching end of Tianjingshan paleo- uplift, is a favorable district toprospect middle and shallow secondary gas-pools as where is the conjunction of NE-trending and NW-trending deep faults.