天然气水合物热激励法开采模型研究

A study on the seepage model for the exploitation of natural gas hydrate by thermal excitation

根据分子动力学分解理论,建立了天然气水合物热激励法开采数学模型,并在此基础上考虑了逆反应的存在对水合物分解规律和气体在地层中渗流特性的影响.利用有限差分法对压力和温度控制方程进行了数值求解,同时分析了地层压力场和温度场的分布规律、天然气的产量变化特征以及渗透率对它们的影响.计算结果表明,在水合物分解前沿,压力值出现跳跃而温度值达到最低点,天然气的产量随时间呈明显的周期性变化趋势,而且随着时间增长,周期逐渐变长,对渗透率的变化敏感.通过分析比较,计算结果与实验结果吻合很好.

Based on the molecular dynamic decomposition theory,the mathematical model for the exploitation of natural gas hydrate by thermal excitation is established.The effect of the inverse reaction of the natural gas hydrate decomposition in the exploitation process on the decomposition law of the natural gas hydrate and the seepage law of the decomposed natural gas in formation is considered in the model.The pressure control equation and the temperature control equation are solved by finite difference method,the distribution laws of formation pressure and temperature in the exploitation process of natural gas hydrate and the variation law of natural gas yield are obtained,and the effect of formation permeability on them are analyzed.The results show that,in front of the hydrate deposition,the pressure presents leaping and the temperature reaches to the lowest point;the natural gas yield presents cyclic variation tend,and the cycle becomes longer with the increase of the exploitation time;they are all sensitive to the change of the formation permeability.The results tally well with the experimental results in literature [8],which shows the established model and the obtained results are correct and reliable.