Reliable Joule-Thomson (J-T) coefficients of geothermal fluids containing CO2 are important for non-isothermal reservoir flow simulation, well stream simulation, and process simulation. The J-T coefficients of fluids can be experimentally determined. However, it is difficult to conduct laboratory measurements because precise PVT data for cross interpolation is required for accurate estimation of the coefficients. Thus, experimentally measured J-T coefficients of water-CO2 mixtures are almost non-existent. Consequently, it is necessary to estimate J-T coefficients by using an accurate equation of state (EoS); however, programming and running a complicated EoS is not an easy task. Accurate EoS modeling requires many parameters, and finding the right volumetric root could be problematic and is not trivial. This paper presents useful correlations for the estimation of J-T coefficients of water-CO2 mixtures. Isenthalpic expansions are modelled for binary mixtures of water and CO2 at different concentrations by using Gallagher, Crovetto, and Sengers EoS (1993). The EoS implemented in this study predicts both phase equilibrium and volumetric properties accurately for a temperature range of 400-1000 K and a pressure range of 0-100 MPa and 30% mole fraction of CO2. Pure component properties are estimated for water and compared with the ones in the literature. In addition, the effects of temperature and pressure on the J-T coefficients are investigated. The EoS given in this study applies for the temperature and pressure conditions which are limited to the ones encountered in typical geothermal reservoirs, and the correlations are derived based on the results of the EoS. The effect of CO2 content on both the J-T coefficients and the inversion curves is also studied. The proposed correlations are derived in the temperature range of 400-550 K and the pressure range of 8-30 MPa.

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