Experimental measurements of CO2 solubility in salt solutions at high temperatures and high pressures

International audienc

Experimental Measurements of Carbon Dioxide Solubility in Na–Ca–K–Cl Solutions at High Temperatures and Pressures up to 20 MPa

International audienceExperimental CO 2 solubility data in brine at high pressures and high temperatures are needed in different technologies such as carbon dioxide storage or geothermal process. A lot of data have been acquired in single-salt solutions, whereas data for mixed-salt solutions remain scarce. In this study, new carbon dioxide solubility data in salt solutions have been measured. Two synthetic brines have been studied at 323, 373, and 423 K from 1 to 20 MPa. The brine 1 is composed of a mixture of NaCl and CaCl 2 and the brine 2 is made from a mixture of NaCl, CaCl 2 , and KCl. Measurements have been carried out by conductimetric titration. In this study, 6 isotherms presenting 48 new solubility data have been reported. These results have been obtained in an original range of temperature, pressure, and salinity. In these conditions of temperature and pressure, we verified that an increase of the temperature or the salinity involves a decrease of the CO 2 solubility. On the other hand, an increase of the pressure implies an increase of the CO 2 solubility. Then, the obtained results were compared with the values calculated using PhreeSCALE and PSUCO2 models. The comparison between experimental and calculated values revealed a good agreement

Thermodynamic characterization of the liquid-vapor equilibria of CO2 – brines systems under high temperature and high pressure conditions

Cette thèse est financée par Total et par l’agence nationale de la recherche (ANR), elle s’inscrit dans le cadre du projet SIGARRR (simulation de l’impact des gaz annexes injectés avec le CO2 pendant le stockage géologique sur la réactivité des roches réservoirs). L’objectif de la thèse est d’acquérir expérimentalement des points de solubilité du CO2 dans des solutions aqueuses salées de chlorure de sodium et de chlorure de calcium dans des conditions de hautes températures (323K < T < 423K) et hautes pressions (5 MPa < P < 20 MPa) à des salinités élevées (1 à 6 mol/kg).Suite à une synthèse bibliographique sur les techniques expérimentales utilisées pour la détermination de la solubilité du dioxyde de carbone dans les solutions aqueuses, trois méthodes de caractérisation ont été expérimentées : Analyse de la phase aqueuse par chromatographie ionique (analyse en ligne) Estimation de la solubilité à l’aide des bilans matière, des quantités de corps pures injectés initialement dans l’autoclave et des paramètres expérimentaux (masse volumique de la phase liquide, volume molaire de la phase gaz à l’équilibre, volume total de l’autoclave…). Piégeage d’un échantillon liquide dans la soude puis dosage. Une étude de sensibilité a été réalisée sur la méthode d’estimation de solubilité par bilan matière. Cette étude a permis d’identifier le niveau de précision de la mesure du volume de l’autoclave afin d’obtenir des estimations de solubilité fiables et précises à haute pression. Pour la dernière méthode expérimentée (piégeage dans la soude puis dosage), un protocole d’échantillonnage, et deux protocoles d’analyses (titrations) ont été développés ; les échantillons des systèmes CO2-H2O et CO2-H2O-NaCl ont été analysés par dosage pH-métrique et les échantillons des systèmes CO2-H2O-CaCl2 ont été analysés par dosage conductimétrique. 84 points de solubilité ont été obtenus au cours de ce travail dont 45 points complétement originaux. Les données expérimentales obtenues ont été comparées avec les résultats de simulations réalisées par le logiciel PHREEQC avec une base de données Pitzer.dat. Le ‘’salting out effect’’ observé a été évalué pour chaque système dans toutes les conditions de températures et pressions étudiées.This work was supported by Total and ‘’Agence National de la recherche’’ as a part of SIGARRR project (Simulation of the impact of annex gases co-injected with CO2 during its geological storage on the Reservoir-Rocks Reactivity. The aim of the thesis was to obtain experimental CO2 solubility data in salty aqueous solutions of sodium chloride and calcium chloride at different molalities (1, 3 and 6 mol/kg) under high temperature (323K < T < 423K) and high pressure (5 MPa < P < 20 MPa).Following a bibliographical study on experimental methods used for the carbon dioxide solubility determination, three characterization methods were tested: Aqueous phase analysis by ion chromatography Solubility estimation from mass balance, amounts of CO2 and liquid initially loaded into the cell and experimental parameters (density of liquid phase, molar volume of gas phase, and total volume of the equilibrium cell…). A liquid sample trapping in sodium hydroxide solution followed by a titrationA sensitivity study was carried out on the Solubility estimation method from mass balance. This study identified the level of accuracy of autoclave volume measurement to obtain reliable and accurate solubility data high-pressure.A sampling protocol was developed to withdraw aqueous samples and trap them into soda solution at high pressure. Two titration procedures were set up; liquid samples of CO2-H2O and CO2-H2O-NaCl systems were analyzed by potentiometric titration and samples of CO2-H2O-CaCl2 system were analyzed by conductimetric titration. 84 solubility data were obtained during this study, which include 45 new experimental data. Experimental measurement were compared to the results of simulation performed with PHREEQC software using a ‘’Pitzer.dat’’ database.The salting out effect observed was evaluated for each system under all temperature and pressure conditions

Mesures expérimentales de la solubilité du CO2 dans des solutions salées à hautes températures et à hautes pressions

National audienc

Experimental measurements and thermodynamic modeling of CO2 solubility in the NaCl-Na2SO4-CaCl2-MgCl2 system up to 150 °C and 200 bar

International audienceTo face the climate change, the geological storage of CO2 in deep saline aquifers has been gaining interest. This study investigates the CO2 solubility in single-salt solutions containing NaCl, Na2SO4, CaCl2 and MgCl2. In a first part, an experimental campaign has been performed in an instrumented batch reactor. Acid-base and conductimetric titrations were performed. CO2 solubility points were obtained for pressure and temperature up to 20 MPa and 423.15 K. The salting-out effect has been studied (at a same ionic force of 3 mol/kg) showing the following order: SO %,CaCl 2 < SO %,MgCl 2 < SO %,NaCl < SO %,Na 2 SO 4. In parallel to laboratory experiments, a modelling work has been carried out to calculate the gas solubility. The specific numerical tool named PhreeSCALE was used. The activity coefficient has been calculated using the Pitzer formalism. Interaction parameters for the CO2-H2O-MgCl2 and CO2-H2O-CaCl2 systems were optimized successfully

Experimental measurements and thermodynamic modeling of CO2 solubility in the NaCl-Na2SO4-CaCl2-MgCl2 system up to 150 °C and 200 bar

International audienceTo face the climate change, the geological storage of CO2 in deep saline aquifers has been gaining interest. This study investigates the CO2 solubility in single-salt solutions containing NaCl, Na2SO4, CaCl2 and MgCl2. In a first part, an experimental campaign has been performed in an instrumented batch reactor. Acid-base and conductimetric titrations were performed. CO2 solubility points were obtained for pressure and temperature up to 20 MPa and 423.15 K. The salting-out effect has been studied (at a same ionic force of 3 mol/kg) showing the following order: SO %,CaCl 2 < SO %,MgCl 2 < SO %,NaCl < SO %,Na 2 SO 4. In parallel to laboratory experiments, a modelling work has been carried out to calculate the gas solubility. The specific numerical tool named PhreeSCALE was used. The activity coefficient has been calculated using the Pitzer formalism. Interaction parameters for the CO2-H2O-MgCl2 and CO2-H2O-CaCl2 systems were optimized successfully