中上扬子地区地史模拟及其油气地质意义

Geohistory modeling and its petroleum geological significance of Middle-Upper Yangtze area

利用三维盆地数值模拟技术恢复了中上扬子地区地史演化过程,在地史发育特征的基础上,分析了古构造对沉积的控制作用,并阐明了其发育的油气地质意义。结果表明,扬子板块泥盆纪沉积前表现为"隆凹相间"的格局,印支期在扬子地台上形成北东向的"一隆两坳"格局。对比加里东期与印支期的构造格局发现,印支期的川西坳陷基本上位于加里东期乐山—龙女寺隆起之上,印支期的泸州古隆起亦覆叠在加里东期的川南坳陷之上,南充—梁平一带位于构造转换的枢纽带,印支期的石首—宜昌隆起发育在加里东期的江汉盆地北部坳陷上,反映出印支期对加里东期的构造反转现象十分显著。从贯穿四川盆地东西向和南北向的2条构造演化剖面也可以看出,印支期对加里东期构造的叠加和反转,并反映出古构造的形成与迁移过程。泸州古隆起是一个典型的印支期古隆起叠加在加里东期古坳陷上的构造,形成了下生上储的油气资源配置关系,对以志留系为源的油气勘探应该具有良好的前景。乐山—龙女寺古隆起和黔中古隆起是印支期以前奥陶系以下地层油气运移的持续指向区,但它们仅能控制寒武系烃源岩的油气,与寒武系生烃坳陷相邻的古斜坡部位油气勘探比较有利。

The 3D basin modeling technique was used to restore the geohistory evolution process of Middle-Upper Yangtze area. Based on geological development characteristics,the control of paleo-tectonic on sedimentary was analyzed to point out its geological significance for hydrocarbon generation. The results show that depressions and uplifts developed alternately in the Yangtze area before Devonian sedimentary period,and an uplift and two depressions of north-east striking developed in Yangtze platform during Indo-Chinese epoch. Through comparing the structures developed in the Caledonian period and in Indo-Chinese epoch,Chuanxi depression developed in Indo-Chinese epoch locates on the Leshan-Longnüsi uplift developed in the Caledonian period. Luzhou paleo-uplift developed in Indo-Chinese epoch superposes on the Chuannan depression developed in the Caledonian period. The zone of Nanchong-Liangping locates in structure transform regions and the Shishou-Yichang uplift develops in north depression of Jianghan Basin,which suggests that the Caledonian strata reversed strongly in Indo-Chinese epoch. The Caledonian structures superposed and reversed strongly in Indo-Chinese epoch showing by the east-west and the north-south structural evolution profiles crossing the whole Sichuan Basin.The Luzhou paleo-uplift,superposed on the Caledonian paleo-depression developed in Indo-Chinese epoch,is a typical upliftwhich could accumulate hydrocarbons generated from the Silurian source rocks below. It could form favorable reservoirs and has good exploration prospect. The Leshan-Longnüsi paleo-uplift and the Qianzhong paleo-uplift are the areas that receive the charge of hydrocarbons coming from the source rocks below until the Indo-Chinese epoch,but they only control the accumulation of the Cambrian hydrocarbons underlying the Ordovician. The paleo-slope adjacent to the hydrocarbon generation depression of the Cambrian source rocks is the benefit zone for hydrocarbon exploration.