浅水流(Shallow Water Flow,SWF)是深水环境海底浅部地层中超压的砂体流动,是对深水钻井最具破坏力的一种地质灾害,严重制约深水油气开发.为有效预测和防治浅水流,需要对浅水流地球物理特性进行研究,并在研究区内加以识别.本文借鉴国外主要深水盆地对浅水流问题的研究经验,对南海北部深水盆地潜在浅水流区域采取以属性判定、超压分析为主,振幅识别为辅的方法进行预测.精细层序地层学解释发现,南海北部深水盆地存在上新世以来的古珠江深水水道沉积体系和第四纪水道,这些水道砂体疏松未固结、孔隙度大、有效应力低、几乎表现出流体特性.基于遗传算法的混合反演方法发现,研究区存在典型的AVO响应,横波速度极低,低频特征明显,振幅强度弱,连续性较好,存在极性反转,高泊白松比和高纵横波速度比.研究结果表明,南海北部陆坡具备浅水流发生的潜在条件,深水水道发育区为潜在的浅水流危险区,浅水流具有独特的地震响应特征,泊松比高达0.49,纵横波速度比约为3.5~9或更高,SWF层位对地震属性的敏感度V_P/V_S>AVO响应>泊松比.
The two-dimensional hydrodynamic model, MIKE21, is applied to simulate the tidal currents and sediment concentration in the radial sand ridges of the South Yellow Sea. Results are in accordance with in situ observations. Then the variations of tidal currents and suspended sediment concentration caused by reclamation and artificial islands projects are simulated. The results show that the impacts are limited around the project areas. After the projects, the fan-shaped, Jianggang centered tidal current pattern would be replaced by a pattern which is formed by two tidal paths. One locates at the Xiyang channel in north-south direction, and the other locates at the Huangshayang channel in east-west direction. The reclamation of Tiaozini separates the waters into south portion and north portion. The changes of sediment concentrations coincide with those of currents. Both the sediment concentrations and tidal currents increase at the northwest of Dongsha and the south of Gaoni, while both decrease at the north and south of Tiaozini, and the east and southwest of Dongsha.