Rock Properties and Sealing Efficiency in Fine-grained Siliciclastic Caprocks — Implications for CCS and Petroleum Industry

Abstract

CO2 sequestration in geological formations is a promising technology and a crucial measure to reduce CO2 emissions across the energy system. It is an essential part of the solution for mitigating climate change caused by anthropogenic greenhouse gases. Three principal criteria are required for the selection of a geological storage site: storage capacity, injectivity, and containment. This dissertation primarily focuses on the CO2 containment and properties of fine-grained siliciclastic caprocks. The outcomes of the research, however, are also partly applicable for injectivity assessments. The dissertation has embraced multiscale approach (pore-, core-, and field-scale), multidisciplinary techniques, and includes a number of carefully selected experimental and analytical investigations. The research contributes to the existing knowledge of caprock sequences and reduces some of the uncertainties associated with the assessment of containment efficiency for geological CO2 storage sites. It also provides answers to some of the less-investigated questions regarding the CO2–brine–rock interactions, and geophysical monitoring during a potential upward leakage of the CO2 plume. The first part of the study explores depositional and compaction trends and their effect on the evolution of rock properties in finegrained clastic sediments. It presents examples from the caprock sequences in the SW Barents Sea and the North Sea. Salt precipitation in the fractured caprocks was the second investigated question. We designed and fabricated a high-pressure high-temperature microfluidic pressure vessel to house geomaterial micromodels. Moreover, we introduced a conceptual framework that suggests salt precipitation is not only a near wellbore phenomenon but also a sealing mechanism that can impede CO2 leakage from the fracture networks. Finally, we have studied how acoustic velocity and electrical resistivity may be influenced by dominant fracture flow of brine–CO2 system to simulate changes in geophysical properties during a potential CO2 leakage. In addition to the carbon capture and storage (CCS), researchers in the petroleum industry, waste repositories, and water resources can also be benefited from the outcomes of this dissertation.