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卢永鑫, 蒋明镜, 王思远. 降压开采下深海能源土近井界面力学特性耦合分析[J]. 岩土工程学报. DOI: 10.11779/CJGE20231245
引用本文: 卢永鑫, 蒋明镜, 王思远. 降压开采下深海能源土近井界面力学特性耦合分析[J]. 岩土工程学报. DOI: 10.11779/CJGE20231245
Coupling analysis on mechanical properties of near-well interface of methane hydrate bearing sediments under depressurization exploitation[J]. Chinese Journal of Geotechnical Engineering. DOI: 10.11779/CJGE20231245
Citation: Coupling analysis on mechanical properties of near-well interface of methane hydrate bearing sediments under depressurization exploitation[J]. Chinese Journal of Geotechnical Engineering. DOI: 10.11779/CJGE20231245

降压开采下深海能源土近井界面力学特性耦合分析

Coupling analysis on mechanical properties of near-well interface of methane hydrate bearing sediments under depressurization exploitation

  • 摘要: 天然气水合物作为最有潜力的清洁能源之一备受关注。开采过程中水合物分解将使近井水合物沉积物(即能源土)力学特性劣化,引起系列开采风险及工程地质灾害。针对目前大多数研究未从微观角度着眼于开采中的能源土-井筒结构接触界面特性变化,本文采用实用型水合物开采多场耦合分析框架TOUGH+HYDRATE+PFC,考虑相对更为真实的能源土-井筒接触界面的不同情况,开展了降压开采多场耦合数值模拟,对近井土体以及井筒本身的力学响应进行了对比分析,探讨了井筒表面粗糙度对于开采中土体、井筒间的相互作用的影响规律。结果表明:①不同井筒表面粗糙程度情况未对温压化及开采效率方面产生明显影响。②适当提高井筒表面的粗糙程度可有效地减小接触土体沉降幅度,增强井壁接触区域土体稳定性,降低开采风险以保证开采能够相对稳定地长期进行。③井筒粗糙度的增大会导致井筒受到更大的摩擦力,需控制井筒表面不能过于粗糙以防止井筒本身受力过大影响而失稳破坏。

     

    Abstract: Methane hydrate (MH) has been attracting extensive attention as one of the most potential clean energy sources. During exploitation, hydrate dissociation induces the weakening of mechanical properties of near-well MH bearing sediments (MHBS), which can result in series of engineering problems. Given that most current researches didn’t focus on the interface properties of MHBS-well structure during exploitation, in this paper, the practical multi-field TOUGH+HYDRATE+ PFC coupling framework is adopted, considering different conditions of a more real MHBS-well interface, the multi-field coupling numerical simulation of depressurization is performed, comparation and analysis are made on mechanical properties of near-well soil and the well, and the influence of surface roughness on wellbore stability is discussed. The results show that: (1) Different well roughness doesn’t have obvious influence on the thermal-mechanical-chemical evolution and production efficiency. (2) Appropriately increasing the surface roughness of the well can effectively reduce the settlement amplitude of the soil in contact area and enhance the stability of soil in the contact area of the wellbore, reduce the risk to ensure a relatively stable long-term production. (3) The increase of well roughness will lead to greater frictional force on the well. It is necessary to control the well surface not to be too rough, in order to prevent the wellbore itself from suffering the impact of excessive forces, losing stability and becoming failure.

     

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