The physical characteristics of a CO2 seeping fault: The implications of fracture permeability for carbon capture and storage integrity

Clare E. Bond, Yannick Kremer, Gareth Johnson, Nigel Hicks, Robert Lister, Dave G. Jones, R. Stuart Haszeldine, Ian Saunders, Stuart M. V. Gilfillan, Zoe K. Shipton, Jonathan Pearce

Research output: Contribution to journalArticlepeer-review

40 Citations (Scopus)
19 Downloads (Pure)

Abstract

To ensure the effective long-term storage of CO2 in candidate geological storage sites, evaluation of potential leakage pathways to the surface should be undertaken. Here we use a series of natural CO2 seeps along a fault in South Africa to assess the controls on CO2 leakage to the surface. Geological mapping and detailed photogrammetry reveals extensive fracturing along the mapped fault trace. Measurements of gas flux and CO2 concentration across the fracture corridor give maximum soil gas measurements of 27% CO2 concentration and a flux of 191 g m−2 d−1. These measurements along with observations of gas bubbles in streams and travertine cones attest to CO2 migration to the surface. Permeability measurements on the host rock units show that the tillite should act as an impermeable seal to upward CO2 migration. The combined permeability and fracture mapping data indicate that fracture permeability creates the likely pathway for CO2 migration through the low permeability tillite to the surface. Heterogeneity in fracture connectivity and intensity at a range of scales will create local higher permeability pathways along the fracture corridor, although these may seal with time due to fluid-rock interaction. The results have implications for the assessment and choice of geological CO2 storage sites, particularly in the assessment of sub-seismic fracture networks.
Original languageEnglish
Pages (from-to)49-60
Number of pages12
JournalInternational journal of greenhouse gas control
Volume61
Early online date12 Apr 2017
DOIs
Publication statusPublished - Jun 2017

Bibliographical note

The authors would like to acknowledge the financial support of the UK CCS Research Centre (www.ukccsrc.ac.uk) in carrying out this work. Author Kremer is supported by NERC grant NE/N015908/1. The UKCCSRC is funded by the EPSRC as part of the RCUK Energy Programme. Midland Valley Exploration are thanked for an academic license for Move. Porosity and permeability analysis were undertaken in the University of Aberdeen Petrophysics laboratory with the aid of Sophie Harland. The South African National Energy Development Institute (SANEDI) Stakeholder Engagement team under the South African Centre for Carbon Capture & Storage (SACCCS) is thanked for making the scientific work possible. The National, Provincial and Local Government structures including Traditional Authorities, Municipalities, landowners and local residents are thanked for granting permission to conduct the monitoring in the areas of interest. CGS staff are thanked for their assistance and support in the field. We thank two anonymous reviewers for their comments, which helped to improve the manuscript.

Keywords

  • fracture permeability
  • CO2 storage
  • leakage
  • natural analogue

Fingerprint

Dive into the research topics of 'The physical characteristics of a CO2 seeping fault: The implications of fracture permeability for carbon capture and storage integrity'. Together they form a unique fingerprint.

Cite this