New insight into prediction of phase behavior of natural gas hydrate by different cubic equations of state coupled with various mixing rules

Progress in hydrate thermodynamic studynecessitates robust and fast models to be incorporated inreservoir simulation softwares. However, numerous modelspresented in the literature makes selection of the best,proper predictive model a cumbersome task. It is ofindustrial interest to make use of cubic equations of state（EOS） for modeling hydrate equilibria. In this regard, thisstudy focuses on evaluation of three common EOSsincluding Peng-Robinson, Soave-Redlich-Kwong andValderrama-Patel-Teja coupled with van der Waals andPlatteeuw theory to predict hydrate P-T equilibrium of areal natural gas sample. Each EOS was accompanied withthree mixing rules, including van der Waals （vdW）,Avlonitis non-density dependent （ANDD） and general non-quadratic （GNQ）. The prediction of cubic EOSs was insufficient agreement with experimental data and withoverall AARD% of less than unity. In addition, PR plusANDD proved to be the most accurate model in this studyfor prediction of hydrate equilibria with AARD% of 0.166.It was observed that the accuracy of cubic EOSs studied inthis paper depends on mixing rule coupled with them,especially at high-pressure conditions. Lastly, the presentstudy does not include any adjustable parameter to becorrelated with hydrate phase equilibrium data.