天然气水合物降压开采理论模型及分析

    The analysis for the theoretical model about the gas production from gas hydrate by depressurization

    • 摘要: 研究天然气水合物分解过程中的温度场和压力场,可以预测天然气产量,为提高天然气的产出效率提供可行方法。在此,对天然气水合物降压开采的轴对称数学模型进行了改进,在分解面上加入了带有水合物相变潜热影响的能量守恒方程,利用波尔兹曼变换方法严格推导出解析解。通过数值方法求解常微分方程初值问题,得到了水合物分解前沿的精确位置。最后,根据数值算例,给出了压力场温度场的分布以及天然气的产量与时间的关系,分析了井筒压力对分解面移动速度的影响。结果表明,水合物的潜热对温度场有一定影响,分解面附近温度会降低;降低井口压力,会明显提高天然气的产出速率。

       

      Abstract: By doing research on the fields of pressure and temperature in the process of gas hydrates decomposition, we can predict the output of gas, and can provide feasible ways to increase the efficiency of gas production. The axisymmetric mathematical model is improved about the gas productions from hydrate by depressurization, the energy balance equation is employed considering the effect of the latent heat of gas hydrate at the decomposition front, the analytical solution is introduced by the method of Boltzmann transformation. The exact location of the gas hydrate decomposition front is obtained by solving initial value problems of ordinary differential equations through numerical method. Finally, the distribution of pressure and temperature fields and natural gas production with time are given according to numeric calculation example, the impact of the well bore pressure on the speed of the decomposition front is analyzed. The results show that the latent heat of gas hydrate has effect on the field of temperature, the temperature near the decomposition front is lower, the rate of gas production can be raised by reducing the pressure of well.

       

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