Subsurface Aspects of CO2 sequestration: Lessons learned from major CCS projects and numerical investigations

Abstract

To honor the Paris Agreement in decreasing greenhouse gas emissions, this thesis looks into carbon dioxide (CO2) sequestration as an unavoidable path to lower these emissions and limit rising global temperatures. After analyzing the subsurface characteristics of more than fifty-one CO2 sequestration projects, two major problems seem to stir the attention of the research community, notably storage low and heterogeneous permeability conditions, and the destiny of injected CO2 over long periods. Permeability, injection rate, and depth of storage are important indicators for the longevity of the injection. Nevertheless, low permeability reservoirs have proven to be very successful, notably with projects like Yanchang and CNPC Jilin in China (L. Wang et al., 2017) having permeability in the order of 1 mD. We performed numerical simulations using the TOUGH3 simulator, to assess the impact of permeability on the CO2 sequestration process. The permeability range considered in this study is 0.1 to 1000 mD. On the other hand, five different heterogeneous structures were analyzed to assess the impact of heterogeneity and permeability. Injection scenarios involving injection over 30 years and 50 years, coupled with a post-injection observation over 1000 years were considered. CO2 occupied a percentage pore volume ranging from 1 to 10% both benchmarked by the International Energy Agency (IEA/EEC) report on CO2 Storage Capacity Assessment Methodologies for Saline Aquifers (Gorecki et al 2009)