华北板块东南缘海相层系演化特征及油气远景

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的气源通道断裂;推覆体之下的下寒武统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属大陆边缘沉积,其发育的海相泥质烃源岩具有高碳,高Ro,高Tmax和低氯仿A的特点,已进入热演化的过成熟阶段;北淮阳型石炭系处于前陆盆地的沉积中心,地层序列齐全,其煤系源岩有机质丰度高,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可能潜在良好的勘探前景。因此,进一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。

Evolution and hydrocarbon potential of the marine strata on the southeastern margin of the North China plate

The combustible gas and burned tunnels founded in the Dabie orogenic belt are concentrated to the North Dabie complex zone south of the Mozitan-Xiaotian fault and the Early Carboniferous metamorphosed quartz schist close to the Xinyang-Shucheng fault. The two faults have provided gas source pathways which are connected to deeper reservoir rocks. The Lower Cambrian Fengtai Formation below thrust nappes and the North Huaiyang Carboniferous strata, both of which occur as the marine source rocks, are considered as the main gas source rocks of the tunnel combustible gas. The Lower Cambrian Fengtai Formation consists of the continental marginal deposits, in which the marine muddy source rocks have been in an oversaturation stage of thermal evolution characterized by high carbon, high Ro, high Tmax and lower chloroform-bitumen ＂A＂. The North Huaiyan Carboniferous source rocks have high abundances of organic matter with the III-type kerogen and high thermal maturation, resulting in the generation of abundant hydrocarbons. The discovery of the tunnel combustible gas indicates that the deep-seated marine strata in the Hefei Basin may be highly prospective for oil and gas resources. The future exploration should be carried out from the Mesozoic and Cenozoic basin systems to the deep-seated marine strata, with the emphasis on the ＂Palaeozoic source rocks and Palaeozoic reservoir rocks＂ or ＂ Palaeozoic source rocks and Cenozoic reservoir rocks＂.