水合物开采引起的地层稳定性三场耦合分析

Coupled deformation-flow-thermal analysis of soil during gas hydrate decomposition

为防止水合物开采引起的地质灾害,采用有限元方法,对abaqus有限元软件进行二次开发,模拟水合物开采过程中的水、热、力三场耦问题,重点分析水合物开采过程中地层应力场和位移场变化规律.结果表明:降压与加热法联合开采水合物时,降低井口压力可以显著提高水合物的分解速率;水合物分解区附近地层孔压明显降低,土体有效应力增加.海床表面会产生较大的沉降和水平位移,并随水合物分解距离的增大而线性增加,当最大分解范围为30 m时,海床表面最大沉降达5 m,最大水平位移达1.6 m.该研究结果为水合物开采时地层及开采平台稳定性的安全评估提供理论指导.

To prevent geotechnical hazards induced by gas hydrate decomposition from happing, this study utilized the secondary development of ABAQUS using the finite element methods, performed the coupled deformation-flow-thermal analysis of soil, and summarized the distribution of the soil stress and displacement field. The research shows that decreasing the well pressure can raise the gas production rate. The effective stress increases significantly with the increasing of pore pressure in the decomposition zone. The seabed subsidence and horizontal displacement increases linearly with the decomposition radius; the maximum subsidence reaches 5.0m and the maximum horizontal displacement reaches1.6m when the decomposition radius reaches 30m. The results can provide theoretic guidance for the security evaluation for the stability of seabed and platform.