【作者】 啜世阳； 王华宁； 郭振宇；

【Author】 Chuai Shiyang;Wang Huaning;Guo Zhenyu;School of Aerospace Engineering and Applied Mechanics, Tongji University;State Key Lab of Disaster Reduction in Civil Engineering, Tongji University;

【机构】 同济大学航空航天与力学学院； 同济大学土木工程防灾国家重点实验室；

【摘要】 天然气水合物是一种清洁、高能效的未来可能替代能源,由于深海水合物赋存形式和赋存的物理化学环境的特殊性,在钻井和开采过程中由于水合物分解带来的储层力学特性劣化等问题使其开采风险和分析难度远远大于传统能源。本研究针对水合物地层钻井过程中的多场相互作用井壁稳定问题,在考虑对流和扩散的基础上结合实际工程背景建立了简化的非稳态温度、压力、浓度场分布函数,以自主建立的温度-压力-盐浓度三维相平衡方程为判据,考虑钻井液侵入和水合物分解对储层物理、化学和力学特性的影响以及多场间的部分相互作用,基于水合物储层特有的与反压、温度、水合物饱和度相关的屈服准则(Mohr-Coulomb屈服准则基础上修正),通过解析的方法对水合物井壁进行了理想弹塑性轴对称平面问题力场解答的推导,并进行了力学机理和参数的分析。研究结果有助于揭示水合物地层钻井风险的控制机理。更多还原

【Abstract】 Natural gas hydrate is a clean and energy efficient alternative energy in the future. There are a lot of hydrate resources to be developed in South China Sea. However, due to the particularity of the occurrence form and physical and chemical environment of deep-sea hydrate, the mining risk and analysis difficulty of hydrate decomposition in drilling and mining are much higher than that of traditional energy. Aiming at the stability of multi-field coupling borehole wall in the drilling process of hydrate formation, this study independently established three-dimensional phase equilibrium equation and simplified distribution function of unsteady temperature, pressure and salt concentration field. The effects of drilling fluid intrusion and hydrate decomposition on the physical, chemical and mechanical properties of the reservoir as well as the partial interactions between multiple fields are considered. Based on the yield criterion(modified on the basis of the Mohr-Coulomb yield criterion), which is unique to hydrate reservoir and related to back pressure, temperature and hydrate saturation, the mechanical field solution of the ideal elastic-plastic axisymmetric plane problem of hydrate wellbore is deduced by analytical method. The mechanical mechanism and parameters are analyzed. The research results are helpful to reveal the control mechanism of drilling risk in hydrate formation.更多还原