注蒸汽开采冻土区天然气水合物数值计算与野外应用

Numerical Calculation of Steam Mining for Natural Gas Hydrate Exploitation in Permafrost Region and the Field Application

试开采研究是天然气水合物从理论研究走向商业化开采的必经之路。提出的注蒸汽开采是一种综合开采方法,是在降压开采的基础上,往孔内注入热蒸汽对水合物目标开采层进行激振往复式热激发。注蒸汽开采能够避免"自保护效应",促进水合物进一步分解,理论上能够扩大开采范围、提高产气量。利用FLUENT数值模拟软件对蒸汽加热水合物层动态过程进行数值计算,通过模拟计算结果对比分析,在满足开采要求的前提下确定最佳的注蒸汽功率为20 kW,注热时长为38 h。在青海木里盆地天然气水合物试采项目中,注蒸汽开采进行了5.2 h开采试验,产气量为3.25 m3。

The trial mining of gas hydrate is the only way which must be passed from the theoretical research to commercial exploitation.The steam mining is a combine mining method.Based on the pressure relief mining, hot steam is injected to the hole for thermal excitation in the gas hydrate target layer, which can avoid “self-preservation effect”, promote further decomposition of the hydrate and expand mining area theoretically.Numerical calculation was done on the dynamic process of steam heating hydrate layer by FLUENT software.Through the comparative analysis on the simulation results, it was de-cided that the best steam power was 20kW and the heat injection time was 38 hours in order to meet the requirements of the premise mining.In the natural gas hydrate production project in Muli basin of Qinghai, the steam mining lasted for 5.2 hours with the gas production of 3.25m3 .