Thermophysical properties of CO2 aqueous solutions and the impact of H2S on CO2 storage

Abstract

Carbon Capture and Storage (CCS) is one of the best possible options to manage the produced CO2 from the development of high CO2 hydrocarbon fields or from any other CO2 sources. Pure CO2 with impurities free injection into a suitable formation reservoir must be properly designed to avoid unnecessary CCS operational issues. From the technical perspective, knowledge of the thermophysical properties of the fluid is essential to ensure safe and efficient capture, transport and storage of CO2 in the reservoir formation for permanent storage. There are available studies completed on these CCS fluid thermophysical properties and impurities which can be found elsewhere in the literature. However, due to the massive variety of the possible compositions of the captured CO2 with a different type of impurities that could present, along with different operating ranges of pressure, temperature and brine compositions in CCS operation, new and further experimental data for the thermo-physical properties are necessary. In this study, new CO2 solubility data in different type of aqueous solutions were generated using high-pressure high temperature (HPHT) experimental setup from HWU PVT laboratory. Further investigation accessing the impact of H2S on the CO2 solubility were also completed at temperatures and pressures up to 423 K and 25 MPa respectively using Vapour Liquid Equilibrium (VLE) setup from the Centre of Thermodynamic Processes (CTP), Mines Paris Tech. The measured results were compared against in house predictive model, along with the available experimental data from the open literature. In addition to this, density and viscosity of the CO2 aqueous phase over geological sequestration conditions, pressures up to 80 MPa and temperatures up to 423 K were also investigated. An oscillating U-tube densitometer method and capillary tube viscosity techniques via HPHT setup from HWU was used in determining both fluid densities and viscosities, respectively. The new density and viscosity results measured in this work were validated against the calculated density and viscosity model predictions. Apart from filling the literature gaps, the new thermophysical data generation will help to validate the existing equations of state (EoS) thermodynamic model predictions and act as an input to improve the existing reservoir model accuracy. New CO2 solubility profile (with H2S present) was incorporated into the existing reservoir model to access the impact of the H2S presence in the injected CO2 stream on CO2 storage.