水下沉箱冲淤特性模型实验研究  

Model experiment study on scouring and depositing characteristics around subsea caissons

作　　者：李书兆 沈晓鹏 李伟 段明印 唐国强[2] 杨帆 LI Shuzhao;SHEN Xiaopeng;LI Wei;DUAN Mingyin;TANG Guoqiang;YANG Fan(CNOOC Research Institute Ltd.,Beijing 100028,China;State Key Laboratory of Coastal and Offshore Engineering,Dalian University of Technology,Dalian,Liaoning 116024,China)

机构地区：[1]中海油研究总院有限责任公司,北京100028 [2]大连理工大学海岸和近海工程国家重点实验室,辽宁大连116024

出　　处：《中国海上油气》2023年第3期217-226,共10页China Offshore Oil and Gas

基　　金：中海石油(中国)有限公司科技课题“渤海油气田水下生产系统国产化研究与示范(编号:CNOOC-KJ 135 ZDXM 36 TJ 07 ZY)”部分研究成果。

摘　　要：水下沉箱是渤海通航区水下生产系统的重要防护装置,但海流冲刷作用可能导致沉箱暴露,使其面临被渔业活动、船舶抛锚等破坏的风险。为支撑渤海浅水水下生产系统水下沉箱方案设计,以某实际工程闭口型水下沉箱为例,通过物理模型实验,研究沉箱凸出高度、回填砂与原场砂等对沉箱冲淤特性的影响。实验中考虑海床面与沉箱顶面相对位置的不同,设置了凸出式、齐平式(沉箱顶面与海床表面齐平)与掩埋式3种水下沉箱模型实验,研究沉箱在不同掩埋情况下其周边海床土层的冲淤特性。结果表明,闭口型沉箱顶部高于海床面或与海床面齐平时,沉箱来流方向上游发生了局部冲刷,下游则出现了不同程度的淤积,且淤积高度随沉箱凸出高度增大而增大;对于掩埋式沉箱,回填沙在极限流速下会被完全冲走,但原场砂会重新回填、淤积并覆盖沉箱;但如果上游泥砂量供给不足,随着时间发展,沉箱周围的泥砂将被冲刷并导致沉箱暴露。综合模型实验结果,建议该工程使用齐平式或者掩埋式闭口沉箱形式。本研究为水下生产系统水下沉箱的设计提供了参考。Subsea caisson is an important protective device for subsea production system in the navigation area of the Bohai sea.However,the scouring effect of ocean currents may cause the caissons to be exposed,causing the damage risk by fishing activities,ship anchoring,etc.To support the design of subsea caisson scheme for shallow water subsea production system in the Bohai sea,a physical model experiment was conducted to study the effects of caisson protrusion height,backfill sand,and in-site sand on the scouring and depositing characteristics around a closed subsea caisson in a practical project.In the experiment,considering the different relative positions of the seabed surface and the top surface of the caisson,three types of subsea caisson models,namely protruding,flush(the top surface of the caisson is flush with the seabed surface),and buried were set up to study the scouring and depositing characteristics of the soil layer at the seabed around the caisson under different burial conditions.The results show that when the top of the closed caisson is higher than or flush with the seabed surface,local scour occurs upstream in the direction of the incoming flow of the caisson,while different degrees of deposition occur downstream,and the height of deposition increases with the increase of the protruding height of the caisson;for buried caisson,the backfill sand will be completely washed away at the limit flow rate,but the in-situ sand will be backfilled,silted up,and then the caisson will be covered;if the upstream sediment supply is insufficient,the sediment around the caisson will be washed away and cause the caisson to be exposed with the time process.Based on the comprehensive model experiment results,it is recommended to use a flush or buried closed caisson form for this project.This study provides a reference for the design of subsea caissons in subsea production system.

关 键 词：渤海浅水水下生产系统 水下沉箱 模型实验 局部冲刷 泥砂输运 

分 类 号：TE54[石油与天然气工程—油气田开发工程]