南海东北部陆坡区天然气水合物成矿作用

摘要

The northeastern slope of the South China Sea has the characteristics of the passive continental margin in Cenozoic and has many oil and gas bearing basins. As a result, the geological and tectonic settings, the temperature and pressure conditions, and the methane-generating potential from the thick organic-rich sediments are all favorable for gas hydrate formation. Through the studies of structure, deposit, gas sources, gas hydrate phase equilibrium and thermodynamic conditions, this paper discussed the favorable situations for gas hydrate formation in the northeastern slope of the South China Sea. The results show that the seafloor temperature, geothermal gradient and stress conditions are favorable for gas hydrate forming; there are special tectonic settings,such as diaper, mud volcano, and slope-fault structure combination; the shallow layers have suitable lithological characteristics and high deposition rate; there are abundant biodegradation gas and thermal-genetic gas. Therefore it comes to the conclusion that the study area is a hydrate prospective area.%南海东北部陆坡区具有准被动大陆边缘构造特征,新生代含油气沉积盆地发育,具备天然气水合物发育的一系列有利地质构造背景.基于该区已有的调查资料,从构造、沉积、成矿气体来源和水合物相平衡及其热力学特征等方面,综合分析了南海东北陆坡区有利的天然气水合物成矿条件.结果表明,研究区完全具备形成水合物的海底温度、地温梯度和压力条件,存在底辟和泥火山构造、斜坡-断层构造组合等特殊地质构造环境及构造部位,浅部沉积层具有合适的岩石学条件和较高的沉积速率,并存在丰富的生物气和热解气.因此,南海东北部陆坡区具有潜力极大的天然气水合物成矿远景.