天然气的加速式二次运移过程研究

在静水条件下,游离相天然气运移的主要动力是浮力,阻力是毛细管力。根据前人的实验数据,通过理论计算发现,浮力和毛细管力均受地层温度和压力的影响,气体在储层中上浮的临界高度随地层温度和压力的降低而增大。根据气体状态方程及天然气运移的动力学理论,推导出温度和压力降低前、后气体流速比方程,用其计算了不同储层中临界气体长度并分析不同储层中相同长度的气体在运移途中的变化规律。由此发现,在运载层物性不变的情况下,天然气沿上倾地层向上倾方向运移的过程,是随地层温度和压力不断降低、其运移速度逐渐增大的过程,如果有后续气体的加入,会使气体长度增大,致使运移速度增加得更快。

Research on Speedup Process about Natural Gas Secondary Migration

Main driving force for migration of separate phase natural gas is buoyancy,and resistance is capillary force.According to previous experimental data,it is found that the buoyancy and capillary force are effected by reservoir temperature and pressure,and the boundary height of natural gas coming-up so on.The boundary height of natural gas coming-up is accreting along with the reservoir temperature and pressure decreasing.Based on natural gas state equation and dynamic theory of natural gas migration,natural gas velocity of flow rate equation before and after temperature and pressure decreasing is fetched,and with which interface natural gas lengths in different reservoirs are calculated and the changing law of equivalent-length natural gas in migration is analyzed,whence it is discovered that migrating velocity of natural gas along tilting up reservoir is increasing inch by inch,along with temperature and pressure continuously decreasing.If other natural gases join,the natural gas length would increase,and the migrating velocity of natural gas would increase more quickly.