A SAFT Equation of State for the H2S-CO2-H2O-NaCl System and Applications for CO2 - H2S Transportation and Geological Storage

Abstract

When H 2 S is co-injected with CO 2, we need to know thermodynamic properties and phase equilibria for the CO 2 -H 2 S-H 2 O-NaCl system in order to evaluate the storage capacity, optimal transportation and injection conditions, potential for pipeline corrosion, and increased risk of storage and leakage. Here, we summarize the results of the phase equilibrium and densities for CO 2 -sequestration related systems from a thermodynamic model that is based on statistical associating fluid theory equation of state. The proposed thermodynamic model can be used to represent equilibrium compositions in both phases (H 2 O-rich/aqueous phase and gas-rich/non-aqueous phase) and the density at equilibrium or in the one phase region. The effect of H 2 S impurities on the properties of CO 2 streams and on the CO 2 solubility and the corresponding aqueous solution density can be predicted to provide a knowledge base for both transportation and geological storage. In addition, as other ions such as Ca, Mg, K and SO 4 have been taken into account in our model, the properties for brine in geological reservoirs in addition to simplified aqueous NaCl solutions can also be predicted. The equation of state from this study can be incorporated into reservoir simulators to model the separation of phases in multi-phase flow and fluid reactions with reservoir rocks.

A screening criterion for selection of suitable CO 2 storage sites

“…The aqueous solution (saline water) density can be quantified using the approach presented by Ji and Zhu (2013). In this case, Interfacial tension between CO 2 and brine can be estimated using Chalbaud's approach which gives an appropriate estimation when pressures and temperatures are in the range of 45 to 255 bars, and 71 to 100 o C respectively (Chalbaud et al, 2009).…”

Determination of CO2 Solubility in Water and NaCl Solutions under Geological Sequestration Conditions Using a Fused Silica Capillary Cell with in Situ Raman Spectroscopy

“…In order to estimate the total amount of CO 2 that can be stored in a reservoir, it is necessary to accurately access the solubility of CO 2 in H 2 O and in brine under reservoir conditions. In addition, it is also necessary to understand the details of the numerous CO 2 -related geological processes occurring in the reservoir. , …”

Comparison of corrosion behaviors of low‐alloy steel exposed to vapor‐saturated H2S/CO2 and H2S/CO2‐saturated brine environments

“…The coupons were originally weighted using a balance with precision of 0.01 mg. The test solution was 3.5 (mass%) NaCl according to previous studies .…”

“…The impurities influence the CO 2 corrosion of steel. H 2 S gas is the main impurity in CO 2 stream and 3/4 of the cost is used for CO 2 separation . The injection of CO 2 and H 2 S into CCS sites is regarded as preferred approach to reduce capture and separation cost.…”

“…The injection of CO 2 and H 2 S into CCS sites is regarded as preferred approach to reduce capture and separation cost. Many studies have shown that H 2 S causes corrosion of pipeline steels . The corrosion of low‐alloy steels exposed to H 2 S/CO 2 environment is different from the one exposed to pure CO 2 environment because the physical and chemical properties of CO 2 and H 2 S are different.…”