De-risking top seal integrity - Imaging heterogeneity across shale-dominated cap rock sequences

Abstract

The below-ground geological storage of CO2 is seen as an important component to the long-term reduction of global greenhouse gas emissions. One of the difficult tasks is to find large storage locations with good seals (“roofs”) that prevent any stored CO2 from leaking back to the atmosphere. Leaking fluids typically follow fractures, cracks and more permeable (“open”) routes as they bypass rocks that are tighter. Such local variations contribute to geological complexity, and their study is important to geological CO2 storage. This doctoral work revolved around the use of emerging digital technologies, computer models, and drones to investigate the impact of geological complexities on fluid flow in Svalbard. Studies in Svalbard benefit from the archipelago’s unique outdoor laboratory that makes it exceptionally for analogue studies; Little vegetation makes for excellent outcrops, and a wealth of existing data can be integrated to solve complicated questions. Surface features are frequently used as analogues for “invisible” processes underground as they can more easily be catalogued and interpreted. This doctoral work did precisely that and used detailed surface information to investigate the potential impact of geological complexity on the fluid flow below ground. The resulting findings were then used to assess the current state of fluid leakage in central Svalbard, aided by dedicated studies of gas leakage and gas hydrate occurrence in the fjords. As Svalbard has a shared geological history with large parts of the Norwegian continental shelf, these findings are of regional importance.