上扬子三江地区中新生代构造变形的油气地质意义

上扬子地台是我国南方的海相油气富集区, 其周缘地区分别处于不同的构造带中, 构造变形差异显著, 致使海相油气的盖层和保存条件各异.在揭示上扬子三江地区中新生代构造变形特点的基础上, 结合岩相古地理和油气成藏要素的演化, 探讨后期构造活动对海相油气分布和高原低熟油气形成的控制.研究认为, 印支运动的推覆挤压破坏了早期的海相生储盖组合, 同时也导致山前带挠曲下陷, 发育新的成藏组合.燕山运动期间, 在稳定的盆地裂陷过程中沉积了一套区域性海泛湖相泥岩, 既是优质源岩, 也是有效的区域盖层.在白垩纪至古近纪的盆地萎缩过程中, 发育了区内最重要的景星组(K₁j)储层, 以及古近系膏泥岩层, 该套地区性盖层对高-过成熟的裂解气有重要保存意义.新近纪以来, 强烈的走滑断陷和高原隆升过程对海相油气的后期保存十分不利, 同时, 控制了一系列小型山间断陷盆地的形成, 这些盆地陆源和水生有机质都佷丰富, 在低热演化阶段, 源岩遭受微生物降解, 形成未熟-低熟油气, 尽管该类油气资源有限, 但对于青藏高原低演化油气的勘探有所借鉴. 

The Petroleum Geological Significance of Meso-Cenozoic Tectonic Deformation in the Sanjiang Region of Upper Yangtze Block

The upper Yangtze platform of South China is rich in marine oil and gas. As located in different tectonic zones, its adjacent areas have distinct deformation styles, which leads to various cap rock and preservation conditions of marine hydrocarbon. Based on revealing the Meso-Cenozoic tectonic deformation characteristics of Sanjiang region in upper Yangtze block, and combined with the evolution of lithofacies and hydrocarbon accumulation factors, this paper discusses on the process that post-tectonic events controls on the distribution of marine hydrocarbon and formation of low mature oil & gas in plateau. It is suggested that early marine source-reservior-cap assemblages were destructed in Indo-China movement which resulted in growth of new reservoir forming assemblages in foreland subsidence as well. During the time of Yansinan movement, the basin rifting led to marine-flooding lacustrine mudstone deposition, not only acting as excellent source rocks, but also as regional cap rocks. From Cretaceous to Paleogene, the reservoir rocks of Jingxing Formation (K₁j) and plaster rock grew in the process of basin atrophy. The critical cover of plaster rock is very important to marine over mature cracked gas. After Neogene, the strong strike-slip activity and plateau uplift has been unfavorable to the later preservation of the marine oil and gas, controlling the formation of a series of small mountain intermittent depression basin which are rich in land-based sources and aquatic organic matter, and the source rock are subjected to microbial degradation, generated immature-low mature oil and gas in low thermo evolution stage. This type of oil and gas resources is limited, but it provides a reference for the low evolution oil and gas exploration of the Tibetan Plateau.