The Effects of CO2 on Reservoir and Seal Quality during Storage in Depleted Rotliegend Gas Fields in NE Netherlands

The effects of CO2 storage on reservoir quality and caprock integrity have been studied for several potential storage sites in northeast of the Netherlands. These fields have the Permian Rotliegend as the reservoir, overlain by Zechstein carbonates, anhydrites and salt. Long term laboratory experiments were carried out in high pressure/ temperature condition on reservoir and seal samples in the presence of CO2, methane and brine. The results were then compared with the predictions from model simulations. Experiments and modeling results are in good agreement with respect to the nature of mineral dissolution and precipitation. However, deviation between modeling and experiment is observed with regard to the magnitude and time scale of changes in mineral dissolution and precipitation. In many observed experimental cases, both processes appear to occur more aggressively (i.e. faster and stronger) than predicted by the model. The probable reason for this deviation is uncertainty in the key modeling parameters such as activation energy and surface area of minerals. Exact knowledge of the brine composition is also essential.