南海北部井场调查中常见的海洋灾害地质

Marine Geohazards at the Well Sites in the Northern Part of South China Sea

南海北部准被动大陆边缘自第四纪以来具有较强的新构造运动,由此形成的各类潜在地质灾害对于迅速发展的海洋油气资源勘探开发,是一项值得认真研究的课题。20世纪80年代至今,在南海北部承担了大量的井场调查和研究,结果表明南海北部灾害地质因素类型很多,危险性较大或分布较广的是活动断层、地震、滑坡、沙波、浅层气和埋藏古河道,它们的发育受区域地质环境控制。南海新构造运动东部强于西部,北部强于南部,东北部最强。在水深50～130m左右,深部构造较稳定,具有活动能力的破坏性地质灾害类型较少,限制性地质条件如埋藏古河道广泛分布,侵蚀沟、浅槽和凹凸地等十分发育,是南海北部相对稳定的区域。在水深大于130m,是陆架转向陆坡的过渡带,各种具有活动能力的地质灾害类型,如断层带、大型滑坡带、陡坎、底辟及沙波等普遍存在,地震活动多,地形复杂,是南海北部不稳定区域。

New strong tectonic movements are existed at quasi-passive continental margin, northern of South China Sea in Quaternary. All types of potential geohazards, which are formed in this period, become concerned issues during the rapid development of marine oil and gas ex- ploration. A lot of regional investigation and well site surveys have been carried out in wide area of North of South China Sea from 1980 till now. The results indicate that the potential geohazards can be divided into 12 types, which distribute over different regions. In 50 - 130m water depth, the active geohazards are few but non-active restricting geological conditions are completely de- veloped, such as buried paleo-channel, erosion groove, erosion trough, and concavo-convex, et al. The exterior continental shelf is relatively a steady region. The active geohazards are widely developed under 130m water depth, such as fault, sandwave, sliding mass, muddy ground outcropped and scarp. The earthquake activity is increasing, and topographty of seabed is much more complex. So the shelf edge-upper continental slope is sea bottom which is the most unstable region.