天然气水合物开采区内海床不均匀沉降对管道力学性能的影响

Influence of uneven seabed subsidence on mechanical properties of pipeline in natural gas hydrate mining area

海底管道是天然气水合物大规模开采和集输的关键装备。天然气水合物的开采过程会扰动沉积层的结构,改变沉积层的强度和力学特性,诱发海床发生不均匀沉降,并对水合物开采区内海底管道的力学特性产生影响,如引起管道发生大变形、悬跨、屈曲、断裂等。基于ABAQUS有限元软件,建立天然气水合物开采区内"海床-管道"耦合作用模型,模拟了天然气水合物开采过程中海床沉降变形及其对管道应力、应变、弯矩、悬跨等力学行为的影响。研究结果表明,在天然气水合物开采过程中,海床的不均匀沉降将引起管道发生显著位移并发生弯曲,管道的应力、应变随着变形的增大而增大。当海床沉降量达到某一程度时,管道将脱离海床,产生悬跨,并引发涡激振动风险。

Submarine pipeline is the key equipment for large-scale exploitation and gathering of natural gas hydrate.The mining of natural gas hydrate will disturb the structure of the sedimentary layer,change the strength and mechanical properties of the sedimentary layer,and induce the uneven subsidence of the seabed.It will have a great impact on the mechanical properties of the submarine pipeline in the hydrate mining area,causing large deformation,suspension span,bucking and crack of pipeline.ABAQUS finite element software was used to establish the seabed and pipeline coupled action model in the natural gas hydrate mining area,and the subsidence and deformation of the seabed and their influence on the mechanical behaviors of the pipeline,such as stress,strain,bending moment and suspension span,were simulated.The results show that in the process of gas hydrate exploitation,the uneven subsidence of seabed will cause the pipeline to displace and bend significantly,and the stress and strain of the pipeline will increase with the increase of deformation.When the subsidence of the seabed reaches a certain degree,the pipeline will leave the seabed and generate suspension span,and cause a vortex induced vibration risk.