Determination of Diffusion Coefficients of Etgane in Water at Higg Pressure and Temperature witg In-Situ Raman Spectroscopy
Lin Linlin
Guo Huirong
Hao Xuan
Huang Yiqi
Abstract：Ethane and methane are two main components of natural gas.Accurate diffusion coefficients at high temperature for ethane and methane are the key to calculate the diffusion and fractionation of gases in deep natural gas reservoirs,especially in unfractured shale and other geological materials with low permeability.However,the diffusion coefficients for ethane at pres-sures and temperatures near the reservoir conditions are scarce in the literature.In this study,diffusive transfer of ethane in water at 20 MPa and from 273 to 393 K was observed in a high-pressure optical capillary cell via Raman spectroscopy.Diffusion coefficients were then determined by the least-square method.The relationship between diffusion coefficients [D(C2 H6 )in m2/s]and temperature (T in K)was derived with Speedy-Angell power-law equation as:D(C2 H6 )= D0 [(T/Ts )- 1 ]γ,where D0 = 13.805 5 × 10- 9 m2/s ,Ts = 237.4 K ,γ= 1.739 7.The diffusion coefficients of ethane are much smaller than those of methane at the same condition.The amount of methane and ethane diffused through some thick low permeability layers are cal-culated and the results show that such diffusivity difference can cause a significant fractionation of methane and ethane in thick shale layer.
Keywords：ethanemethanepure waterdiffusion coefficientRaman spectroscopydiffusion amount
Publication Date：2014-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：9( 1584-1592 )