天然气水合物加热开采的热力学分析

摘要

The one-dimensional model is improved considering the effect of gas hydrate latent ,an axisymmetric mathematic modeling is developed for the gas production by heating .Free boundary value problem is solved using Boltzmann-transformation and the analytic solutions for temperature field is obtained .New idea is adopted to solve the non-linear problem caused by the gas hydrate latent ,the functional relationship between the location of decomposition front and time is obtained by solving initial value problem for system of ordinary differential equations ,more accurate results is obtained .The results show that there is great temperature gradient near the well ;The thermal efficiency is improved and the gas generation rate is decreased as the well temperature is increased ;The thermal efficiency is improved with the increasing of the dissociation radius at a certain well temperature .New method has theoretical significance ,the numerical results has practical significance for increasing thermal efficiency and the gas generation rate from gas hydrate .%考虑水合物相变潜热的影响，对一维模型进行了改进，建立了水合物加热开采时地层温度场分布的轴对称数学模型。利用玻尔兹曼变换方法求解了水合物分解引起的动边界问题，推导出模型的解析解。在处理水合物相变潜热引起的非线性问题上，采用新的求解思路，通过求解常微分方程的初值问题，得到分解面的位置与时间的函数关系，其结果更为精确。计算结果表明：在井筒附近温度梯度较大，在离井筒较远区域，地层温度变化不明显；降低井口温度，能够使水合物开采的热效率提高，水合物的产气速率降低；在井口温度一定时，热效率随着分解半径的增大而增加。新的求解方法具有一定的理论意义，数值计算结果对提高合物开采的热效率及天然气产出速率具有实际指导意义。