天然气扩散系数的实验研究

EXPERIMENTAL STUDY ON THE DIFFUSION COEFFICIENTS OF NATURAL GAS

在分析天然气扩散系数测定原理的基础上 ,作者自行组装了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 ,并能较好地模拟地层条件。利用该仪器分别测定了天然气通过 13块人造石英粉砂岩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确定了对实测天然气扩散系数进行饱和介质条件转换的转换系数为6 .0 6。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。这是因为随着埋深增加、地温升高天然气分子运动速度加快的缘故 。

Based on the analysis of the measuring principle of natural gas diffusion coefficients,the authors assembled by themselves a temperature-controllable measuring apparatus of natural gas diffusion coefficients.This apparatus can determine the natural gas diffusion coefficients of rocks under the conditions of high temperature and high pressure,and can well simulate the conditions of strata.By use of this apparatus,the diffusion coefficients of natural gas when it passes through thirteen dried artificial quartz siltstone samples and water-saturated rock samples are determined separately.Using the integral formula of the Fick Law and the Van der Waals Equation of gases,it is determined that the conversion coefficient of measured natural gas diffusion coefficients in the conversion of medium-saturated conditions is 6.06.The measured diffusion coefficients of natural gas is corrected in temperature by the Stocks-Einstein Equation.After correction,the natural gas diffusion coefficients under the conditions of strata are all smaller than measured values,and the difference between them decreases gradually with burial depth.This is because that the movement of natural gas moleculars is accelerated with the increase of burial depth and geotemperature.It indicates that the corrected results ard fit for the conditions of strata.