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Strategies for Environmental Monitoring of Marine Carbon Capture and Storage

Periodic Reporting for period 3 - STEMM-CCS (Strategies for Environmental Monitoring of Marine Carbon Capture and Storage)

Reporting period: 2019-03-01 to 2020-02-29

Carbon dioxide Capture and Storage (CCS) has been identified as an important mitigation strategy to reduce anthropogenic carbon dioxide (CO2) emissions and combat the rising levels of atmospheric CO2 responsible for global climate change and ocean acidification. CCS is seen as a key contribution to reducing anthropogenic greenhouse gas emissions by 2050 and keeping climate change derived temperature increases below 2°C. Offshore storage of CO2 in depleted oil/gas reservoirs and saline aquifers is the preferred option for most European nations.

STEMM-CCS was an ambitious research and innovation project on geological CO2 storage that aimed to deliver new insights, guidelines and tools for CO2 storage at offshore CCS sites. The ability to predict, detect, monitor, and quantify CO2 leaks from sub-seafloor CCS reservoirs is crucial for driving deployment. The project has delivered comprehensive knowledge, technologies and techniques to facilitate:

• Offshore CO2 storage site selection
• Undertaking risk assessments
• Monitoring CCS operations
• Identification/quantification of fluxes from a leak

A controlled release of CO2 beneath the surface sediments was carried out at the Goldeneye reservoir (North Sea). This allowed the demonstration of techniques for CO2 detection and quantification using advanced sensors and novel techniques. The most extensive set of environmental baseline data for the Goldeneye area was collected and generated, and determined the role that existing geological features could play in providing leakage pathways above storage reservoirs.

The work performed during the STEMM-CCS project has advanced our understanding of the complex issues surrounding offshore CCS. STEMM-CCS has worked directly with industry to develop tools and approaches that can be used in the commercial scale operation of offshore CCS. The STEMM-CCS project has allowed a step-change in the confidence that should any leakage occur in future offshore CO2 storage sites, it can be detected, attributed and quantified.
The STEMM-CCS project has successfully achieved all of its goals. Using data collected on a large number of research cruises, the most extensive characterization of the marine environment in the Central North Sea has been produced, compiling geological, hydrographical and chemical data for the area. This has enabled the identification of further data that are needed to fully understand the complex North Sea environment. Application of advanced computer models has allowed identification of the temporal behaviour of key biogeochemical features of the North Sea.

STEMM-CCS carried out one of the world’s most ambitious in situ experiments, successfully performing a controlled release of CO2 to simulate a low-level leak from a storage reservoir. This experiment was performed at a water depth of 120m in the North Sea above the Goldeneye hydrocarbon reservoir, a proposed site for CO2 storage.

The project advanced a suite of in situ sensors, including the most accurate and sensitive total alkalinity sensor ever produced. Techniques for automated analysis of images for baseline surveys were also advanced and published and a number of papers were published on the advancement of the models used and developed in the STEMM-CCS project.

Two geophysics cruises gathered seismic data over an existing chimney structure in the North Sea and the area over the Goldeneye storage complex. A third cruise performed the first drilling of a North Sea chimney structure, acquiring long sediment core samples from the Scanner pockmark in the North Sea. These data allow predictions about the role existing geological chimneys may have in the potential leakage of CO2 from storage reservoirs in the future.

Novel engineering approaches were used for the main release experiment equipment including: a bespoke drill rig from Cellula Robotics, to insert pipes below the seabed to release the CO2 at the right depth and location for the study; a system to place 3 tonnes of CO2 onto the seabed safely, linked to the release pipes and under the control of the ship above; and, upgrading a commercial AUV to increase its capability, allowing more measurements of the chemical and physical environment during its photo imaging surveys of the seabed.

The project has generated interest from scientific, policy and public communities and has presented at a large number of international CCS and technology fora. STEMM-CCS partners are on the advisory boards of projects in the USA and have growing links with Norwegian, Japanese and Australian funded projects.
STEMM-CCS has made advances in key areas that currently limit the demonstration and operation of safe and environmentally sound CO2 storage in offshore geological reservoirs. The solutions for detection, quantification and monitoring are innovative and include products with significant commercial potential. The following have been advanced beyond current state of the art:
• Resolution of natural and anthropogenic induced CO2 permeability of reservoir overburden.
• Observational techniques and models enabling efficient baseline acquisition.
• Cost effective tools for detection and quantification of CO2 leakage.
• Habitat and ecological mapping tools for large-scale high-resolution photography and acoustic mapping.
• Models for various reservoir leak morphologies and decision support tools for mitigation and remediation.
• Assessment of anthropogenic CO2 leaks against natural CO2 fluxes across sediment-water interfaces.

The controlled release of CO2 into sub-seabed sediments at the Goldeneye site allowed the first thorough testing of techniques used for the detection and quantification of CO2 fluxes to the marine environment.

Techniques and technologies to assess and monitor existing and planned offshore CCS sites did not previously exist. STEMM-CCS has delivered approaches that will allow risk and baseline assessment of sites and monitoring of operations, including:
• Three novel techniques to quantify fluxes of CO2 into marine systems using eddy correlation and gradient flux approaches and the use of inert and reactive tracers.
• Integration of new high precision pH and O2 sensors in benthic landers, ROV’s and AUVs
• A new use of a stoichiometric approach to distinguish anthropogenic from natural sources of CO2 in marine systems.
• Novel acoustic technologies for autonomous quantification of gas fluxes
• Optimised technologies for automated benthic image annotation for CCS mapping applications
• Decision support tools for site selection, monitoring system design, site operation and mitigation/remediation actions.

A suite of the in-situ LOC sensors developed during the STEMM-CCS project are in the process of being commercialised through a spin-out company from the NOC, while the optode technology developed by TU Graz is being commercialised by Pyro Science.

The technologies and tools that STEMM-CCS has delivered will facilitate large scale deployment of CCS and increase the confidence of CCS operators and regulators to conduct cost effective surveys allowing compliance with legislation. This work can be used to promote CCS as a CO2 mitigation strategy and build on the existing lead that Europe has in developing offshore CCS. The project has used extensive knowledge sharing across the global CCS community and is informing proposed developments in the USA, Australia and Japan.
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