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Gorgon CO2 Surface and Near-surface Monitoring

Hortle, A., George, S.J., Noble, R.R.P., Falter, J., Hardman-Mountford, N.J., Harris, B., Stalker, L., Sutton, J. and McInnes, B.I.A. (2013) Gorgon CO2 Surface and Near-surface Monitoring. CSIRO


This report is a review of the current status of the various techniques used to monitor the near-surface environment above a GCS (geological CO2 storage) project, with specific reference to Barrow Island. The review covers a range of environments, broadly sub-divided into near-surface atmospheric, soil gas, groundwater and the near-shore and marine environment. For each environment the key parameters likely to be indicative of migrant CO2 (including CO2 directly) are considered. The techniques covered include geochemical, isotopic, geophysical, microbial, marine and near-surface atmospheric. For each technique what parameters are measured, the effectiveness of each, the stage of development, relative cost and footprint and some of the practicalities of implementing such a system on Barrow Island are described. Included in the report is a review of where these technologies are being deployed or researched at different GCS sites around the world. There are few commercial scale GCS projects, the majority are demonstration scale and the monitoring techniques being applied are as much for technology development as leakage detection. One of the major difficulties with a near-surface environmental monitoring system is the need to be able to demonstrate detectability of a small or non-existent signal within an inherently noisy system. There are potentially many ways to detect CO2 or parameters affected by its presence; however, they need to be coupled with a method to quantitatively distinguish them from the background environmental or anthropogenic variability. For each of the technologies reviewed, three common themes emerged. The first is that no single technology is likely to meet all of the monitoring objectives. The need for targeted, high intensity monitoring sites at high risk locations should be coupled with lower resolution, larger scale monitoring at low risk sites. There are technologies that are appropriate for each of these; small scale (centimetre to metres) continuous monitoring, such as soil gas or geochemistry and those more suited to periodic, regional scale characterisation and monitoring such as the airborne geophysical techniques (10's of kilometers). Some of the near-surface ambient techniques may be suitable for intermediate scale monitoring of several kilometers. The second theme is the need for modelling studies supported by field trials and data collection to quantify the effects and therefore the detectability of each parameter that may be affected by CO2. The modelling would be used to identify the areas of high risk or high uncertainty and form the foundation for building the monitoring system. The third theme is the need to collect baseline data at least one year prior to injection beginning. The collection of baseline data is fundamental to building the models and understanding the natural variation of the system, including emission sources. However, the collection of baseline data is a non-trivial exercise, particularly on Barrow Island. Each of the potentially suitable techniques would require further field based studies to determine their most effective instrument set-up and measurement resolution. Finally, the technology associated with GCS near-surface monitoring is evolving rapidly. Instrument sensitivity, data sampling rates, equipment deployability, deployment costs and processing/interpretation methods are undergoing rapid change. The monitoring system deployed on Barrow Island will need to be flexible and adaptable to account for changing conditions and technologies.

Item Type: Report
Series Name: Technical Report. EP133044
Publisher: CSIRO
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