Variation Of Soret Coefficients Under Different Geothermal Gradients

The migration and distribution of oil and gas components are mainly affected by factors such as gravity differentiation and the Soret effect.Under the effect of geothermal gradients,the Soret effect will weaken the effect of gravity and affect the composition distribution.Carrying out the measurement research of Soret effect and Soret coefficient will help to predict the distribution of reservoir components more accurately.This dissertation studies the thermal diffusion behavior of n-pentane and n-heptane mixed solutions in different temperature gradients and porous media through laboratory experiments and molecular dynamics simulation.First of all,using the experimental system based on gas chromatography technology,the concentration distribution of n-pentane and n-heptane mixed solution under the action of temperature field is obtained,n-pentane tends to aggregate at the high temperature end,n-heptane tends to aggregate at the low temperature end.Then,by fitting the concentration distribution data,the Soret coefficients under different temperature gradients and porous media environments are calculated.The Soret coefficient increases as the temperature gradient increases,the more dense the reservoir,the smaller its value.Finally,Coarse-grained molecular dynamics simulation method was used to analyze the pure thermal diffusion process without the influence of gravity.The results show that the n-pentane particle group still tends to aggregate in the high temperature region,and the n-heptane particle group tends to aggregate in the low temperature region.The Soret coefficient value of the components increases with the increase of temperature difference,which is consistent with the experimental results.