Dynamic viscosity estimation of hydrogen sulfide using a predictive scheme based on molecular dynamics

An approach based on molecular dynamics results on Lennard–Jones spheres is proposed to model the viscosity of hydrogen sulfide, H₂S. The molecular parameters, that have a strong physical meaning, are the depth of the potential, and the length at which the potential is null (the “molecular diameter”), which take into account the dipolar moment of the hydrogen sulfide through an isotropic dipolar approximation. The interest of the method is that the adjustment does not involve any viscosity data because only density values have been used in order to estimate the molecular parameters. Consequently, the model is entirely predictive. A comparison between the data generated by our model, REFPROP7 and REFPROP8 database and the few available experimental viscosity data (dilute gas and saturated liquid) is performed and it clearly demonstrates the performance of this predictive model. It is even shown that this model is, without fitting, slightly better than REFPROP7 and REFPROP8 which uses viscosity experimental database to adjust their parameters. In addition, in typical petroleum reservoirs conditions, it is shown that non-negligible deviations appear when comparing results predicted by REFPROP7, REFPROP8 and the model proposed. Due to its predictive nature, we believe that the values evaluated by the proposed model make sense in such reservoir conditions, at least for industrial purposes. Moreover, the scheme proposed is shown to be very easily extended to deal with mixtures involving H₂S with the limit that the Lennard–Jones fluid model is appropriate for the other species of the mixtures.