EXPERIMENTAL STUDY ON THE DIFFUSION COEFFICIENTS OF NATURAL GAS

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.