Overburden Analysis and Seal Integrity Study for CO2 Sequestration in the North Sea (OASIS)
OASIS (Overburden Analysis and Seal Integrity Study for CO2 Sequestration in the North Sea) is a research project funded by the Research Council of Norway under the CLIMIT programme. The CLIMIT programme is a Norway's national programme for research, development, piloting and demonstration of CO2 capture and storage (CCS) technologies for power generation and other industrial sources.
Figure: Map showing three potential CO2 storage sites of Smeaheia, Heimdal and Utsira in the North Sea (left). The depth map of the Sognefjord Formation (the main sandstone reservoir in the Smeaheia area, Source: Gassnova) based on a combination of the low density 2D seismic and high density 3D seismic interpretations (right). (See better version)
About the project
In the OASIS project we will focus on Smeaheia area (one of the three potential sites that evaluated by Equinor) which has been appointed the full-chain CO2 storage site for the federal NORCCS project (See figure).
The objectives of the OASIS project are:
- To suggest a seismic data derived 3D geomechanical model focusing on the overburden and seal rocks. For geomechanical input the dynamic elastic moduli will be directly computed from the seismic inverted volumes, whereas static elastic moduli will be computed using statistical relations. Uncertainties in the geomechanical input due to lack of the information will be treated as probabilistic input for the simulation for a quantitative risk assessment. The input will be precisely adjusted by additional information such as well log, geological information, geomechanics lab data etc.
- To develop a comprehensive understanding of the interactions between geophysical and mechanical behavior of CO2 storage formation and cap rock.
- Use combined information to predict various risks involved with the injection and storage of CO2 i.e. the present state of stress in the study areas, presence of critically stressed faults, assessment of safe pressure level to avoid leakage by seal damage, or through fractures and/or fault movement under perturbation of pore pressure, predict injection pressure, and direction of induced fracture in case of injection pressure goes above the formation/seal integrity etc.
For a safe CO2 storage, the seal above a potential reservoir and the overburden are extremely important. The seal rock integrity and the overburden rocks will be analysed for the proposed CO2 storage site "Smeaheia" in order to identify critically stressed faults to predict slip on potential active faults as a function of pore pressure change or build-up, evaluate risk for fracturing, and risk of vertical and lateral CO2 migration. This makes the project directly applicable and of benefit to existing and future large-scale CO2 storage projects on the Norwegian Continental Shelf (NCS).
Reliably determining distribution and predicting future movement of CO2 underground continue to be challenging, but are necessary in the planning and managing of current and future CO2 storage projects. In terms of seal and overburden, the following information are required in order to ascertain a safe CO2 storage:
- Sufficient thickness of the overburden
- Sufficient thickness of the seal/cap rock
- Mechanical strength and integrity vis-a-vis injection pressure
- Degree of brittleness of the seal/cap rock
- Present pore pressure and stress regime within the overburden
- Presence of fracture and fault location and orientation
- Critically stressed faults
- Possible thermos-chemical interaction of CO2 with the seal rock
- Direction of CO2 plume migration, and
- Well integrity (not in present study) and optimum well trajectory through the overburden.
The project’s objectives will be achieved by an interdisciplinary research involving laboratory experiments, petrophysical-geophysical analysis and theoretical/computational modelling. To address project objectives, the research activities are subdivided into three work packages (WP) that deal with seal and overburden characterization (WP1), G&G work (WP2), and geomechanical modelling, calibration and iterations, predictions and sensitivity analysis (WP3).
The seismic data coverage provides us with information from the surface down to a depth below the potential reservoir. Therefore, it can be an excellent source of information of the overburden and seal rock, such as presence and orientation of faults and fractures etc. From seismic inversion the overburden seal-rock characterization information (i.e. brittleness, fluid, sedimentary facies etc.) can be obtained. Furthermore, dynamic elastic moduli obtained by seismic inversion can be used as input to a field scale 3D geomechanical model.
The project will be carried out as a collaborative effort between the University of Oslo (UiO), Norwegian Geotechnical Institute (NGI), Norwegian Computing Center (NR), Curtin University (CU), National Oceanography Centre (NOC), Colorado School of Mines (CSM) and two industry partners TOTAL and Equinor. It will involve experience and young scientists from all partner institutions and will recruit 1 Researcher, 1 PhD Research Fellow and 3 MSc students who will work on the different tasks under the mentorship of the Senior Researchers. The combined knowledge base and track record of the senior and young scientists, and their dedicated integrated efforts, warrant leading edge results from the project.
- Department of Geosciences, University of Oslo (UiO), Norway
- Curtin University (CU), Perth, Australia
- Colorado School of Mines (CSM), Golden, CO, USA
- Norwegian Computing Center (NR), Oslo, Norway
- Norwegian Geotechnical Institute (NGI), Oslo, Norway
- National Oceanography Centre (NOC), Southampton, UK
CLIMIT programme / Research Council of Norway. Project: 280472
Additional funding: Equinor and Total
Project duration: 1st August 2019 to 31st January 2022 (three and a half years).