南海天然气水合物开采海底沉降预测

Prediction of Seabed Settlement Caused by Natural Gas Hydrate Exploitation in South China Sea

利用有限差分软件FLAC3D,模拟了温度-应力-流体三相耦合条件下不同开采方法时海底的沉降,比较了延长加热时间和提高开采温度时海底沉降范围。分析得出,距离开采井一定范围内的区域是开采引起沉降的主要区域,由于天然气水合物分解对天然气水合物层强度降低的影响很小,导致天然气水合物层强度降低的主要原因是与生产有关的排水所致;同时,神狐海域天然气水合物开采中,延长加热时间对沉降的影响比提高开采温度产生的影响明显,即延长加热时间的影响范围要比提高开采温度时的影响范围大。

By using the finite difference software FLAC3 D,the seabed consolidation settlement behavior with different mining methods is simulated under the condition of thermal-stress-fluid three-phase coupling.The ranges of seabed settlement when the heating time was prolonged and the exploitation temperature was increased were compared.The results of the analysis show that the main area of settlement induced by mining is in a certain range of the mining well and the decrease of NGH layer strength,slightly influenced by NGH decomposition,is mainly caused by production-related drainage.The results also show that in the NGH mining in Shenhu area prolonging heating time has a more obvious influence on the settlement than increasing temperature,namely the influenced area of prolonging heating time is larger than that of improving exploitation temperature.