Evaluation of long-term mineral trapping at the Ketzin pilot site for CO2 storage: An integrative approach using geochemical modelling and reservoir simulation

Abstract

The aim of this work was to quantify long-term mineral trapping at a reservoir scale for the Ketzin pilot site for CO2 storage. An integrative approach coupling geochemical to reservoir simulations was therefore used. The main advantage compared to fully coupled reactive transport simulations is the reduction of computational time. Reactive transport simulations have not yet been performed to validate the approach. Data needed for the numerical simulations is supplied by geophysical and geological investigations at the site as well as by core and fluid sample analysis.The selection of elements of the 3D grid was carried out distinguishing between those exposed to gaseous CO2 and those with only dissolved CO2. Porosity and water saturation were used as coupling parameters between geochemical and reservoir simulations. An analytical approximation to scale geochemical simulations for heterogeneous porosity and water saturation was developed to assign each selected element of the reservoir model a dynamic and unique mineral trapping scenario. This was crucial to ensure the effectiveness and precision of the approach.Geochemical simulations show that mineral trapping is consecutively taken over by siderite, dolomite and magnesite, whereby the effective rate of mineral reactions strongly depends on the porosity. Results at reservoir scale after 10,000 years yield continuous growth of mineral trapping with an amount of 17,000tonnes, which is about 25% of the totally injected CO2.