水合物注热开采影响下海底斜坡动态稳定性评价  

Dynamic stability evaluation of submarine slopes with hydrate reservoir under influences of heat injection exploitation

作　　者：年廷凯[1] 宋晓龙 张浩 荣泽 NIAN Ting-kai;SONG Xiao-long;ZHANG Hao;RONG Ze(State Key Laboratory of Coastal and Offshore Engineering,Dalian University of Technology,Dalian 116024,China)

机构地区：[1]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：《岩土工程学报》2022年第12期2167-2176,I0025,共11页Chinese Journal of Geotechnical Engineering

基　　金：国家自然科学基金项目(52079020&51879036);辽宁省兴辽英才计划项目(XLYC2002036)。

摘　　要：注热开采会破坏水合物储层的温压平衡,引发水合物分解、储层孔隙压力激增,进而可能诱发海底斜坡沿水合物层发生失稳滑动甚至大规模海底滑坡,因此研究开采影响下水合物储层的动态响应和海底斜坡实时稳定性十分重要。首先推导了一种考虑热-水-化(THC)耦合作用的实时超孔压求解格式,建立水合物饱和度与超孔压之间的内在关系;进一步,基于无限坡极限平衡理论,发展水合物注热开采下海底斜坡动态稳定性的简化评价方法,并开发相应的数值模拟及计算程序。利用该方法对中国南海北部陆坡第二次水合物试采区开展了深入分析,探究了注热开采过程中海底斜坡的温度剖面、水合物饱和度剖面和动态稳定性安全系数等演变特征,并提出了合理化的开采建议。研究成果为深刻认识水合物分解引起的海底斜坡失稳破坏机理、实现水合物的安全可持续开发和海洋地质灾害风险的科学评估提供了重要依据。The heat injection exploitation will destroy the temperature and pressure balance of hydrate reservoirs,cause hydrate dissociation,lead to the dramatic increase of pore pressure of strata,and then induce the instability of submarine slopes along the hydrate reservoirs or even a large-scale submarine landslide.Therefore,it is very important to investigate the dynamic response of the hydrate reservoirs and the real-time stability of the submarine slopes after environmental changes.First,a solving equation for calculating the real-time excess pore pressure considering thermo-hydro-chemical(THC)coupling is derived,and the internal relation between the hydrate saturation and the excess pore pressure is also established.Further,a simplified evaluation approach for the dynamic stability of the submarine slopes under the influences of heat injection exploitation of the hydrate reservoirs is proposed based on the theory of infinite slope limit equilibrium analysis,and the corresponding numerical simulation and calculation code are developed.This approach is employed to analyze the submarine slope in the second hydrate extraction area on the northern continental slope of the South China Sea.The evolution characteristics of the submarine slopes in the process of heat injection exploitation of the hydrate reservoirs,such as the temperature profile,hydrate saturation profile and dynamic stability factors,are explored,and the reasonable mining suggestions are put forward.The research results provide an important basis for understanding the mechanism of instability of submarine slopes caused by hydrate dissociation,realizing the safe and sustainable development of the hydrate reservoirs and the scientific assessment of marine geological disaster risks.

关 键 词：水合物开采 海底斜坡动态 稳定性 THC耦合 超孔压演化 南海北部陆坡 

分 类 号：TU432[建筑科学—岩土工程]