A simple model for the prediction of CO2 solubility in H2O-NaCl system at geological sequestration conditions

Carbon dioxide (CO2) released in the atmosphere is the principal cause of the so-called global warming or greenhouse phenomenon. One procedure for the mitigation of CO2 consists of the capture, transport and geological storage (sequestration) of the gas in deep saline aquifers. In this work, a model for predicting CO2 solubility in H2O-NaCl system covering conditions typically encountered in geological sequestration (e.g., 300-500 K, 50-2000 bar, and 1-4 mol salt/kg) has been developed and validated by comparison with available experimental and theoretical data. The model is a simple one with four adjustable parameters that is based on an extension of the well-known Setschenov model [K-gs/K-g0 = (P/P-0)(f(Tr,m)) with f(T-r,m) = (0.461 + 0.078 m) (-1 + T-r/(1.0 + 0.1267 m)]. The model is developed by exploiting interesting features in the behavior of solubility data of CO2 in saline water over the above-mentioned ranges of conditions. The model is capable of predicting CO2 solubility in saline water with accuracy comparable to that made by multi-parameter models (having 20 parameters or more). It is also in very good agreement with the available experimental data with root-mean-squared-error (RMSE) in the range of 0.03-0.225 mol CO2/kg H2O. The extrapolative power of the model is acceptable at both ends of its range of applicability. (C) 2010 Elsevier B.V. All rights reserved.