REACTIVE TRANSPORT MODELLING FOR CO2 STORAGE IN SALINE AQUIFER AT IN SALAH

The injection of CO₂ from natural gas production, commenced operations in 2004 with a injection rate approximatlely one million tons per year. Based on the chemical data from experiments designed to assess change of formation mineralogy in response to the addition of supercritical CO₂, a multi-phase reactive transport model is constructed to simulate the CO2 transport and water chemistry evolution in the storage formation. The injection continues 5 years and then stops. 5 years after the injection, the pH around the injection well drops to 3.9 (background pH is 5.6). 100 years after the CO₂ injection, the plume of gas phase CO₂ still maintain around the injection well. 500 years later, the plume of CO₂ extends and can spread to another plume of injection CO₂. Because the decrease of pressure, the plume of pH almost maitains after 500 years, even though the plume of CO₂ moves. The dissolution of Fe minerals increases the concentration of aqeous Fe in the water. Simulation results indicate that most sequestered CO₂ is in the form of siderite. The results of reactive transport modelling provide valuable insights for analyzing the behavious of injected CO₂ and assessing the storage sites.