中文摘要：

我国南海的天然气水合物（以下简称水合物）90%以上都属于非成岩矿体,常规方法难以开采。周守为院士创新性提出了高效开发该类水合物矿体的革命性技术之一——固态流化法,并在中国南海神狐海域依托国内自主知识产权的技术、装备和工艺等,成功试采了该类水合物。在流化试采过程中,井底射流破碎水合物矿体至细小颗粒并随钻井液向上返出,含水合物固相颗粒在温度升高、压力降低至受施工参数影响的、区别于常规静态相平衡曲线的动态相平衡状态时发生分解,使得环空液固流动变为复杂气液固多相流动,井控安全要求极高,需要对施工参数优化设计。为此,基于目标区块工程地质特征并结合复杂井筒多相流动分析,对该工程参数进行优化设计,建立了复杂介质井筒多相流动、温度、压力以及水合物相平衡、分解理论模型和数值计算方法,通过数值仿真、软件仿真以及实验验证,对不同施工参数下的流化试采井筒多相流动进行了分析,形成了海洋天然气水合物流化试采现场工程参数优化设计方法及方案：井底射流流化井段直径不宜过大,应适当提高钻井液排量、密度、施加井口回压,以保证安全携岩和降低井控风险。该基础理论研究成果为现场施工以及试采产能的提升提供了重要技术保障。

英文摘要：

More than 90% of natural gas hydrates （hereinafter, hydrate for short） in the South China Sea are non-diagenetic ore bodies, so they can- not be exploited easily by means of the conventional methods. In this paper, the solid fluidization method, as one of the revolutionary technologies in efficient exploitation of non-diagenetic natural gas hydrates, was, for the first time, put forward by Academician Zhou Shouwei. And it is success- fully applied s in Shenhu of the South China Sea based on the technologies, equipment and processes which rely on domestic independent intellec- tual property rights. During the production test of fluidization, the ore bodies of hydrates are broken by the jet at the bottom hole into fine particles and carried upward by the drilling fluid. When the phase equilibrium state is reached with the increase of temperature and the decrease of pressure affected by the operation parameters, which is different from conventional phase equilibrium state, the hydrates bearing solid particles are decom- posed, and consequently liquid-solid flow in the annulus becomes complex gas-liquid-solid multiphase flow. Therefore, it is necessary to optimize the construction parameters design so as to meet the high-level requirements of well control safety. In this paper, the engineering parameters are optimally designed based on the engineering geological characteristics of the target block, combined with the analysis on complex multiphase flow in the wellbore. Then, a theoretical model and a numerical calculation method for the multiphase flow, temperature and pressure of complex media in wellbores and the phase equilibrium and decomposition of natural gas hydrates were established. And the multiphase flow in the wellbore during the production test of fluidization was analyzed under different operating parameters by means of numerical simulation, software emulation and ex- perimental verification. And thus, the design optimization scheme of on-site engineering parameters of production test of marine natur