基于实践十号空间实验的石油组分Soret效应研究

This proposal is a subsequent work based on the Europe-China joint project "Research on thermal diffusion and measurement of Soret coefficients of crude oil under microgravity condition" on the board of Shijian-10. In this proposal, based on former outputs from space experiments, we will cooperate further with European colleagues to obtain precise data of Soret coefficients of mixtures with different components in crude oil. Our results will be compared to computer simulations, so as to figure out the difference of thermal diffusion mechanisms between binary mixtures and multi-component ones. Precise data of Soret coefficients measured from current microgravity experiments, combining with the modeling for crude oil reservoir, will also be applied to the new prediction of component distributions in crude oil reservoir. In addition to this cooperation, in China we will also independently perform new researches relevant to molecular dynamics (MD) simulations and experiments. A concept of "thermal-mean path" is proposed in the MD simulation of thermal diffusion (Soret effect) to demonstrate the correlation between the distribution of temperature field evolution and hydrocarbon fractions distribution. Based on this update, more reasonable results of Soret coefficients can be expected. Experimentally, we will study the Soret effect in porous media with multi-surroundings and temperature gradients, so as to better understand the influence of porous media and seepage on the Soret effect, which will also be helpful for improving the modeling for the prediction of component distributions in crude oil reservoir.

本项目是基于实践十号上的中欧合作项目“微重力条件下石油组分的热扩散过程研究和Soret系数的测量”而开展的后续性研究工作。在已获得空间实验数据的基础上，我们将与欧方进一步合作，获得空间微重力实验中不同混合体系的Soret系数的精确数据，并与计算机模拟结果进行对比，以认识多组分与两组分热扩散规律差异的产生机制，还将利用Soret系数的精确数据，结合地底的石油组分分布的建模，来帮助预测石油组分分布。除与欧方的合作研究外，中方还将独立开展后续的分子动力学模拟和实验研究工作。在热扩散过程（即Soret效应）的分子动力学模拟方面，将结合“热均程”概念，来更精确地模拟体系中的温度分布，从而更准确地得到Soret系数。在实验方面，我们还将针对油藏所处的孔隙介质和温度梯度环境，研究孔隙介质中的Soret效应，为认识孔隙介质及孔隙渗透率对Soret效应的影响，以及进一步完善油田中组分分布的建模而提供基础。

本项目是基于实践十号上的中欧合作项目“微重力条件下石油组分的热扩散过程研究和Soret系数的测量”而开展的后续性研究工作。通过继实践十号空间实验之后与欧方的进一步合作，得到了不同混合体系中与热扩散过程及Soret系数相关的热扩散比等参量，通过实验与计算机模拟结果的对比，得到了多组分与两组分热扩散过程的联系，并利用空间微重力实验得到的相关参数，结合地底的石油组分分布的建模，给出了Soret效应对地底石油组分分布的影响规律，发现Soret效应甚至会超过重力效应，使得地底越深位置的油藏密度越低。由于空间实验中二元体系发生泄漏，中方还独立开展了二组分体系Soret系数的分子动力学模拟工作，得到了C5和C7混合体系在不同温度梯度下的Soret系数，为实践十号的科学数据提供了重要的补充。鉴于空间实验的体系中无孔隙介质，中方还独立在地面常重力环境开展了不同孔隙率介质中的热扩散的实验研究工作，发现烷烃组分在多孔环境下的热扩散过程要弱于体相环境，模型渗透率越低，烷烃组分的热扩散过程越弱。相关结果对于提供石油多组分的Soret系数的数值，以及进一步完善油田中组分分布的建模和认识地底石油组分分布规律具有重要价值。