天然气水合物开采的土力学问题：现状与挑战

有效确定含天然气水合物（以下简称水合物）沉积物的工程力学特性并厘清其随水合物分解过程的变化规律，是实现水合物安全、高效开采的前提和保证。为此，围绕水合物开采过程所涉及的关键土力学问题，从物理力学特性的关键测试技术、沉积物的力学特性、含水合物沉积物的物理力学模型、水合物开采过程土力学多场耦合数值模拟等方面，分析和评述了国内外最新相关研究现状、存在的缺陷与不足，进而探讨了上述研究方向未来的发展趋势。结论认为,尽管经过20多年来的发展，有关水合物开采的理论、方法和技术均取得了显著的进展，但从岩土力学的角度来看，目前仍然面临着以下挑战：①大尺度含水合物沉积物试样的人工制备；②含水合物沉积物微细观组构的精细探测与定量表征；③组构变化对含水合物沉积物力学特性的影响机理与规律；④开采扰动下，流沙发生的条件及对储层稳定性的影响机制；⑤开采扰动下，多相多组分含水合物储层的多过程耦合问题；⑥水合物分解/生成条件下，含水合物沉积物的本构响应；⑦有关水合物开采过程数学模型的适定性问题；⑧高效稳定的水合物开采过程数值模型的全耦合解法。

Geotechnical problems in exploitation of natural gas hydrate: Status and challenges

Effective determination of the mechanical properties of natural gas hydrate (NGH) bearing sediments and their variations in the process of NGH dissociation is the prerequisite and guarantee for safe and efficient NGH exploitation. Focusing on the key geotechnical problems involved in the process of NGH exploitation, this paper first critically reviewed and analyzed the current state of knowledge from the aspects of experimental technology of physical mechanical behavior, mechanical behavior, theoretical modeling and numerical analysis, and then discussed the future development trend. In conclusion, after over the past two decades of development, significant progress has been made in the theories, methodologies and technologies related to the NGH exploitation, but in terms of geotechnics, many challenges still remain, including: artificial preparation of large-scale NGH bearing samples; fine detection and quantitative characterization of micro- and meso-fabrics in NGH bearing sediments; underlying mechanisms for the influence of fabric change on the mechanical behaviors of NGH bearing sediments; occurrence conditions of drifting sand and its influence on reservoir stability under the disturbance of exploitation; multi-process coupling in NGH bearing reservoirs under the disturbance of exploitation; constitutive response of NGH bearing sediments during NGH dissociation/formation; well-posedness of the mathematical models related to NGH exploitation; and robust fully-coupled numerical solution procedures for the boundary value problems related to NGH exploitation.