Uncertainty in regional estimates of capacity for carbon capture and storage

Mark Wilkinson,Debbie Polson

doi:10.5194/se-10-1707-2019

Abstract

Abstract. Carbon capture and storage (CCS) is a potentially important technology for the mitigation of industrial CO2 emissions. However, the majority of the subsurface storage capacity is in saline aquifers, for which there is relatively little information. Published estimates of the potential storage capacity of such formations, based on limited data, often give no indication of the uncertainty, despite there being substantial uncertainty associated with the data used to calculate such estimates. Here, we test the hypothesis that the uncertainty in such estimates is a significant proportion of the estimated storage capacity, and should hence be evaluated as a part of any assessment. Using only publicly available data, a group of 13 experts independently estimated the storage capacity of seven regional saline aquifers. The experts produced a wide range of estimates for each aquifer due to a combination of using different published values for some variables and differences in their judgements of the aquifer properties such as area and thickness. The range of storage estimates produced by the experts shows that there is significant uncertainty in such estimates; in particular, the experts' range does not capture the highest possible capacity estimates. This means that by not accounting for uncertainty, such regional estimates may underestimate the true storage capacity. The result is applicable to single values of storage capacity of regional potential but not to detailed studies of a single storage site.

Highlights

Geological storage of carbon dioxide (CO2) has been proposed as a potential technological solution to help reduce emissions of greenhouse gases, given the continued use of fossil fuels to meet much of the world’s energy requirements
In order to identify potential storage sites that are worth the investment required for detailed assessment, attempts have been made to characterise regional saline aquifers using this legacy data on both a regional and national scale, e.g. the NATCARB Atlas for the USA and the CO2 Stored database for the UK
The geological uncertainty of a single storage capacity estimate for a storage unit with no other assessment of uncertainty might be in the range of 30 %–245 % of the estimated value or 6 % to 520 % more conservatively

Summary

Introduction

Geological storage of carbon dioxide (CO2) has been proposed as a potential technological solution to help reduce emissions of greenhouse gases, given the continued use of fossil fuels to meet much of the world’s energy requirements. In carbon capture and storage (CCS), the CO2 produced from industrial sources is captured and transported to a geological storage site and injected deep into the subsurface where it is stored indefinitely in the pore space of the rocks. Rock formations where the pore space is filled with brines too saline for useful extraction, offer the largest storage capacity (Holloway, 1997). In order to identify potential storage sites that are worth the investment required for detailed assessment, attempts have been made to characterise regional saline aquifers using this legacy data on both a regional and national scale, e.g. the NATCARB Atlas for the USA (https://edx.netl.doe.gov/geocube/#natcarbviewer, last access: 1 October 2019) and the CO2 Stored database for the UK (http://www.co2stored.co.uk, last access: 1 October 2019). Lack of capacity is one of the highest risks to carbon capture and storage projects (Polson et al, 2012) and uncertainty affects the design of transport and injection networks (Keating et al, 2011; Middleton et al, 2012a; Sanchez Fernandez et al, 2016)

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Discussion

Conclusion