北淮阳构造带可燃天然气的发现与合肥盆地油气远景分析

Discovery of the Combustible Gas in the Beihuaiyang Tectonic Belt and Analysis of Oil-Gas Potential in the Hefei Basin

北淮阳构造带由一系列向北逆冲推覆的构造岩片组成,是建立大别山造山带和合肥盆地构造关系的纽带。在大别造山带内发现的可燃天然气和发生燃烧的隧道具有明显的区域性,集中分布于磨子潭-晓天断裂以南的北大别杂岩带和信阳-舒城断裂附近的早石炭世变质石英片岩中,磨子潭-晓天断裂和信阳-舒城断裂是连通深部气源的通道断裂;推覆体之下的寒武系凤台组和北淮阳型石炭系两套海相烃源岩是隧道可燃天然气的主力气源岩,其中下寒武统凤台组烃源岩具有高碳、高"Ro"、高Tmax、低氯仿"A"的特点,已进入热演化的过成熟阶段;北淮阳型石炭系烃源岩有机质丰度高,以Ⅲ型干酪根为主,热演化程度很高,大量的油气已经生成,最重要的是研究其成烃过程与圈闭配套史的关系。大别造山带隧道可燃天然气的发现展示了合肥盆地区深部海相层系良好的勘探前景,因此下步勘探重心应从"中新生代盆地系统"转移到"深部海相层系",以寻找"古生古储"或"古生新储"类型油气藏为主。

The Beihuaiyang tectonic belt is composed of a series of north-striking thrust slices, and links the Dabieshan orogenic belt and the Hefei Basin together. Combustible gas and burned tunnels founded in Dabie orogenic belt have distinct regional nature, and most of them distributed in complex zone of the north Dabie orogenic belt which located in the south of Mozitan-Xiaotian fault and the gneiss from the Lower Carboniferous which is close to the Xinyang-Shucheng fault. These two faults provide source passage which is connected to deeper reserivor. The Cambrian Fengtai Formation under thrust nappes and the Carboniferous system of North Huaiyang Formation, which are both marine deposits, are the main gas source rocks of tunnel combustible gas. The Lower Cambrian Fengtai Formation has been in an over mature stage of thermal evolution with the characteristics of high C, high＂ Ro＂, high Tm,x and low chloroform ＂A＂; The Carboniferous hydrocarbon source rocks of North Huaiyang type have a high abundance of organic matter while kerogen is dominated by Type III, there has been abundant hydrocarbon generated, thereby the most important thing is to study the correlation between its process of hydrocarbon generation and the correlated trap history. Combustible gas was found in the tunnel of the Dabie orogenic belt, it demonstrated that the deep marine sequence stratigraphy in Hefei basin had a good exploration prospects, so the next step should transfer the focus of exploration from ＂Meso-Cenozoie basin system＂ to ＂deep marine sequence stratigraphy＂, to find the main type of oil and gas reservoirs ＂Paleozoic source Paleozoic reservoir ＂or＂ Paleozoic source Cenozoic reservoir ＂