中上扬子地区早古生代烃源岩沉积环境与油气勘探

Early Paleozoic Sedimentary Environment of Hydrocarbon Source Rocks in the Middle-Upper Yangtze Region and Petroleum and Gas Exploration

中上扬子地区早古生代沉积盆地主要表现为克拉通海相盆地(∈—O2)和发育在克拉通之上的隆后盆地(O3—S)。由于受区域构造作用、海平面变化以及古气候等主控因素的制约,形成了有利于烃源岩生成的沉积环境,奠定了油气生烃成藏的物质基础。早寒武世,中上扬子地区主要表现为浅海环境,沉积了由上升洋流带来的磷质物质以及分布稳定的黑色页岩,以梅树村组和筇竹寺组地层为代表。中晚奥陶世至早志留世,隆后盆地为局限的浅海环境,形成了以晚奥陶世五峰组和早志留世龙马溪组黑色页岩为代表的烃源岩。上述烃源岩的有利相带呈面状分布于中上扬子地区,为该地区的富烃沉积区,是开展中上扬子地区早古生代海相地层油气基础地质调查和油气勘探的重要和首选地区。

The Early Paleozoic sedimentary basins in the middle-upper Yangtze region were mainly cratonic-marine basin（∈—O2） and the back-bulge basin which developed above the cratonic basin（O3—S）.Due to the constraints of the dominative factors such as the regional tectonics,paleoclimate and the eustatic sea level change and so on,the sedimentary environments in favor of the formation of hydrocarbon source rocks were formed,meanwhile the physical foundation for the generation and reservoir of the petroleum and gas hydrocarbon accumulation was also laid.Early Cambrian,the sedimentary environment of the middle and upper Yangtze region mainly appeared as the neritic environment,the substance Phosphorus brought by the ascending currents and stably distributed black shale were all deposited,the stratum of the Meishucun Formation and Qiongzhusi Formation were the representatives.From Middle—Late Ordovician to Early Silurian,the sedimentary environment of the back-bulge basin was the limited neritic environment,where formed the hydrocarbon source rocks,which were represented by the black shale of the Late Ordovician＇s Wufeng Formation and the Early Silurian＇s Longmaxi Formation.The favorable facies belt of the above-mentioned hydrocarbon source rocks taking on the planar distribution in the middle-upper Yangtze region,were the hydrocarbon-rich depositional areas,and also were the major and first choice areas of carrying out basic geological survey and oil and gas exploration in the Early Paleozoic marine stratum in the Yangtze region.