Trapping mechanisms in Johansen Fm.
Anja Sundal of FME SUCCESS got her PhD degree at University of Oslo May 21st, by defending her thesis “Geological reservoir characterization for subsurface CO2 storage – Methodologies for evaluation of reservoir quality and effects of depositional heterogeneities”.
CO2 capture and storage (CCS) is one of several proposed measures for reduction of anthropogenic greenhouse gas emissions. In Norway, sub-surface, geological storage of CO2 storage in deep, saline aquifers is the most prospective option, providing some high emission point sources from (onshore) energy plants or (offshore) hydrocarbon production sites.
Photo: Sundal on Field Work in Utah
Sundal’s PhD work includes, among other efforts, a revision of the depositional model for the Early Jurassic Johansen Formation in the North Sea, which is a CO2 reservoir candidate nominated by Norwegian authorities. Integration of recent seismic data, facies distribution maps and petrographic descriptions provides new insights with respect to CO2 storage capacity in the Johansen Formation.
Based on these findings, a geological reservoir characterization is presented, with focus on geological properties that control physical and chemical processes involving CO2 as a reactive, buoyant fluid. Understanding the relative effect of these trapping mechanisms is important in order to assess the reservoir quality.
Hypothetic CO2 injection in the Johansen Formation and multiphase fluid flow have been simulated in a suite of scenario models in order to investigate the effect of site-typical geological heterogeneities on fluid distributions and dissolution potentials. Geological heterogeneity introduces alternative migration paths and may enhance immobilization and secure storage of CO2. Dissolved CO2 changes the pH in formation water and geochemical reactions occur. The reactivity of the reservoir depends on mineralogy, water chemistry, temperature and pressure.
In this study, geochemical simulations using data from the Utsira and Johansen formations show that carbonatization potential may vary significantly between facies and due to geological heterogeneity. Precipitation as carbonates is considered the safest long-term trapping mechanism for CO2.
Read more about Anja and her work in the FME SUCCESS Annual report 2014