Programme

P.54 -- Poster, VCTP-45

Date: Tuesday, 13 October 2020

Time: 08:30 - 10:00

Elemental and Isotopic Fractionation of Noble Gases by Molecular Diffusion

Phuc Nguyen (1), Cuong Quoc Doan (2), Magali Pujol (3), Guillaume Galliero (4), Hai Hoang (1)

(1) Institute of Fundamental and Applied Sciences, Duy Tan University, Ho Chi Minh City, Vietnam (2) Quang Binh University, Dong Hoi City, Vietnam (3) TOTAL S.A., CSTJF, Avenue Larribau, Pau, 64018, France (4) Laboratoire des Fluides Complexes et leurs Reservoirs, LFCR UMR 5150, Universite de Pau et des Pays de l’Adour, E2S UPPA, CNRS, TOTAL, Pau, France

Noble gases have been widely used as natural tracers to characterize storage, migration and origin of fluids in geological environments. Interestingly, they are chemically and biologically inert under geological conditions, and are so only fractionated by physical processes. Among existing physical processes, particularly, the molecular diffusion process has shown to significantly induce a fractionation between noble gases. Accurate estimate of such fractionation in geological fluids such as water, oil and gas is greatly demanded in geology and petroleum engineering. Thus, this work is devoted to investigate how to accurately predict elemental and isotopic fractionation of noble gases by molecular diffusion in geological fluids. To do so, we have first performed molecular dynamics simulations to compute the elemental and isotopic fractionation of noble gases in some geological fluids such as water, oil and gases in reservoir conditions. Then, capability of simple and predictive models (square-root relation and kinetic relation) to predict these fractionations have been investigated. Interestingly, it has been found that the square-root relation is able to provide a good prediction for elemental fractionation between major noble gas isotopes in all solvents, except for the cases relevant to the major Helium isotope. However, this relation cannot provide good results for the isotopic fractionation. Regarding the capability of the kinetic relation, the isotopic fractionation can be well computed in the gas, but often deteriorates in the water liquid and the oil. Finally, we have proposed a simple and predictive scheme for the isotopic fractionation of noble gases in the dense fluids (water liquid and the oil).

Presenter: Nguyễn Phúc

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