天然气扩散系数的研究方法

Studying method of diffusion coefficient of natural gas.

自行组装了两套可控温型天然气扩散系数测定仪 ,可以测定高温、高压条件下岩石的天然气扩散系数 ,能较好地模拟地层条件 ,比以往国内外常温、常压或较高温度、压力的测量仪前进了一步。利用该仪器分别测定了天然气通过 1 0块干岩样和饱和水岩样的天然气扩散系数 ,并应用费克定律的积分式及气体范德华方程 ,将实测天然气扩散系数转换为饱和介质条件下的天然气扩散系数 ,转换系数为 6.0 9。利用斯托克斯 爱因斯坦方程对实测天然气扩散系数进行了温度校正 ,校正后地层条件下的天然气扩散系数均小于实测天然气扩散系数 ,且随着埋深增加 ,二者之间的差值逐渐减小 ,其原因是地温随着埋深增加而升高 ,天然气分子运动速度加快 ,表明这一校正结果是符合地层条件的。图 1表 2参

Two sets of measuring instrument of controllable temperature type are fitted, which can be used for measuring the diffusion coefficient under high temperature and high pressure. They are much better in simulating the natural gas diffusion of strata condition than the traditional types, which can only measure the common temperature and pressure. Applying the instruments established, the diffusion coefficiens of natural gas of ten rock samples of dry condition and water saturated condition are measured respectively. Therefore, 6.09 , the conversion coefficient of saturation medium of measured diffusion coefficient is determined using Fick regulation and van der Waals equation. Moreover, the temperature correction of measured diffusion coefficient is obtained applying the Stocks Einstein equation. The diffusion coefficients after the correction are all less than the measured ones, and the differential values become less with the increase of depth, which indicates that the molecules of natural gas get more active with temperature increases. This conclusion can well illustrate that the correction result fits the strata condition.