Phase Behavior of CO2 + Hydrocarbon Mixtures for CO2 Sequestration through EOR. First step: Equation of state modeling of binary mixtures

MARTÍN CISMONDI; SABRINA BELÉN RODRÍGUEZ REARTES; JUAN MANUEL MILANESIO; MARCELO SANTIAGO ZABALOY

Trondheim

Conferencia; 6th Trondheim CCS Conference (TCCS-6); 2011

SINTEF (Noruega)

Geologic storage of CO2 through EOR, already in use for example in the U.S., is receiving more attention as a very promising strategy, both technically and economically, for reducing CO2 emissions globally.Phase equilibrium estimations are important for decisions concerning for example whether a specific exploited reservoir is a good candidate for CO2 -EOR or even the design of optimum long-term production strategies for new reservoirs. In particular, the minimum miscibility pressure (MMP) which indicates the minimum pressure necessary to get complete miscibility between CO2 and a given hydrocarbons mixture at a given temperature, is of special interest.The best suited models for this type of calculations are equations of state, and modeling capabilities depend strongly on the type of mixing rules implemented and procedures for the estimation of interaction parameters values. In addition, calculated densities also depend on the type of EOS, essentially on whether it is a two or three-parameter EOS, and the way pure compound parameters are obtained.Binary mixtures of CO2 with n-alkanes, from the lighter to the heavier ones, have been studied by an important number of authors, both experimentally and using different types of models. An important degree of inaccuracy or scatter can be realized when comparing data from different sources, specially for the more asymmetric systems (long chain alkanes). At the same time, modeling studies have generally achieved only partially accurate results in the correlation of phase equilibrium data in wide ranges of temperature and pressure.In this contribution, we present accurate results of predictive correlations for CO2 + n-alkane binary systems in wide ranges of temperature and pressure, based on a three-parameter cubic equation of state (the RK-PR EOS) coupled to Cubic Mixing Rules (CMRs).