In Situ Triaxial Testing To Determine Fracture Permeability and Aperture Distribution for CO 2 Sequestration in Svalbard, Norway

Environ Sci Technol. 2018 Apr 17;52(8):4546-4554. doi: 10.1021/acs.est.8b00861. Epub 2018 Apr 5.

Abstract

On Svalbard, Arctic Norway, an unconventional siliciclastic reservoir, relying on (micro)fractures for enhanced fluid flow in a low-permeable system, is investigated as a potential CO2 sequestration site. The fractures' properties at depth are, however, poorly understood. High resolution X-ray computed tomography (micro-CT) imaging allows one to visualize such geomaterials at reservoir conditions. We investigated reservoir samples from the De Geerdalen Formation on Svalbard to understand the influence of fracture closure on the reservoir fluid flow behavior. Small rock plugs were brought to reservoir conditions, while permeability was measured through them during micro-CT imaging. Local fracture apertures were quantified down to a few micrometers wide. The permeability measurements were complemented with fracture permeability simulations based on the obtained micro-CT images. The relationship between fracture permeability and the imposed confining pressure was determined and linked to the fracture apertures. The investigated fractures closed due to the increased confining pressure, with apertures reducing to approximately 40% of their original size as the confining pressure increased from 1 to 10 MPa. This coincides with a permeability drop of more than 90%. Despite their closure, fluid flow is still controlled by the fractures at pressure conditions similar to those at the proposed storage depth of 800-1000 m.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carbon Dioxide*
  • Norway
  • Permeability
  • Svalbard
  • X-Ray Microtomography

Substances

  • Carbon Dioxide