天然气水合物分解产生的固体结构损伤影响着沉积物的力学行为,建立了考虑损伤效应的温度-渗流-应力-化学的多物理场耦合理论模型,对比验证该模型的可靠性并分析降压幅度、沉积物初始绝对渗透率和沉积物初始孔隙度对水合物损伤及产气规律的影响。结果表明:降压幅度较大会加剧水合物损伤,较快完成分解;高初始绝对渗透率在围压作用下会引起水合物孔隙闭合,抑制损伤产生,降低产气速率;不同初始孔隙度下,水合物损伤变化呈现出“快-慢-快”3个阶段,初期快速分解促进损伤产生,中期产生较大压缩变形抑制损伤产生,后期分解体积大于沉积物压缩变形使得损伤速率再次加快。

The damage of solid structure caused by the decomposition of natural gas hydrate affects the mechanical behavior of sediments. In this paper, a multi-physical field coupling model of thermo-hydraulic-mechanical-chemical considering damage effect was established. The reliability of the model was verified and the effects of depressurization gradients, initial absolute permeability and initial porosity of sediments on hydrate damage and gas production law were analyzed. The results show that larger depressurization gradients aggravates hydrate damage, resulting in the faster completion of decomposition. High initial absolute permeability causes hydrate pore closure under confining pressure, inhibiting damage and reducing gas production rate. Under different initial porosities, the hydrate damage change takes on a “fast-slow-fast” trend. The rapid decomposition in the first stage promotes damage generation; the larger compression deformation in the second stage inhib-its damage generation; the larger decomposition volume than the compression deformation of the sediments in the third stage accelerates the damage rate again.