Impact and detectability of hypothetical CCS offshore seep scenarios as an aid to storage assurance and risk assessment

Jerry Blackford,Guttorm Alendal,Helge Avlesen,Ashley Brereton,Pierre W Cazenave,Baixin Chen,Marius Dewar,Jason Holt,Jack Phelps

doi:10.1016/j.ijggc.2019.102949

Abstract

Carbon Capture and Storage has the potential to make a significant contribution to the mitigation of climate change, however there is a regulatory and societal obligation to demonstrate storage robustness and minimal local environmental impact. This requires an understanding of environmental impact potential and detectability of a range of hypothetical leak scenarios. In the absence of a significant body of real-world release experiments this study collates the results of 86 modelled scenarios of offshore marine releases derived from five different model systems. This synthesis demonstrates a consistent generalised relationship between leak rate, detectability and impact potential of a wide range of hypothetical releases from CO2 storage, which can be described by a power law. For example a leak of the order of 1 T per day should be detectable at, at least, 60 m distance with an environmental impact restricted to less than a 15 m radius of the release point. Small releases are likely to require bottom mounted (lander) monitoring to ensure detection. In summary this work, when coupled with a quantification of leakage risk can deliver a first order environmental impact assessment as an aid to the consenting process. Further this work demonstrates that non-catastrophic release events can be detected at thresholds well below levels which would undermine storage performance or significantly impact the environment, given an appropriate monitoring strategy.

Highlights

Many commentators regard Carbon Capture and Storage (CCS) as an essential component in limiting climate change to 2 °C or lower (e.g. IPCC, 2014), as legislated by the Paris Agreement (United Nations, 2016)
The synthesis of model simulations presented here shows a consistent generalised relationship between leak rate, detectability and impact potential of hypothetical releases from CO2 storage, which can be described by a power law
Given the lack of real-world release events the accuracy of model simulations is hard to assess, many of the models have been extensively evaluated in terms of their general hydrodynamic skill

Summary

Introduction

Many commentators regard Carbon Capture and Storage (CCS) as an essential component in limiting climate change to 2 °C or lower (e.g. IPCC, 2014), as legislated by the Paris Agreement (United Nations, 2016). Successful deployment of CCS depends on demonstrable storage integrity from both a legal (Dixon et al, 2015) and societal point of view (Bradbury, 2012) and a reliable monitoring strategy. Bielicki et al, 2015; EU, 2009), there are reasonably consistent CCS performance regulations that, in general, minimise the acceptable loss from storage, require any loss from the storage complex to be quantified, necessitate an environmental impact assessment and stipulate a fit-for-purpose monitoring strategy (Dixon et al, 2015). Primary monitoring of storage integrity will involve seismic techniques that are capable of imaging storage formations and overburden, but these can be costly to deploy and have limited sensitivity and accuracy (Jenkins et al, 2015). As leakage points are a-priori unpredictable, monitoring must be able to cover relatively large areas

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Conclusion