Study of the settling characteristics of tailings using nuclear magnetic resonance technique

Abstract

The oil sands mining and extraction processes in Canada produce large volumes of tailings that are a mixture of mainly water, clay, sand, chemicals and bitumen. This residue is deposited into tailings ponds where sand settles faster than fine clays which require many years to fully consolidate. Therefore, land reclamation and water recirculation become significant environmental issues. The tailings settling rate depends on particle size, density and surface properties which can be modified by variations in the pH, salinity, and addition of flocculants and/or coagulants. Although plant scale developments have been made to improve tailings settling rates, there is a need for an on-site fast measurement of tailings settling characteristics to determine process modifications. This study uses the nuclear magnetic resonance (NMR) technique to analyse variations in tailings settling properties. The results show the NMR technique has potential as an online application to estimate the lifetime of a pond and to monitor oil sands processing.

Keywords:

• tailings
• oil sands
• settling
• NMR

Acknowledgments

The authors wish to acknowledge the contributions of the staff at the Tomographic Imaging and Porous Media Laboratory, specially Dr. Sergey Kryuchkov and Qingguo Zhang. The advice and aid from Lauren Asplund and Jill Armstrong from Shell Canada are gratefully acknowledged. The collaboration of Dr. Pedro Pereira from University of Calgary is also appreciated. Additionally, the authors wish to acknowledge the Canada Research Chair in Energy and Imaging affiliates (Shell, Nexen, Devon, PetroCanada, Canadian Natural, ET Energy, Suncor, Schlumberger, Laricina, Paramount, CMG Foundation and ConoccoPhillips) and the Natural Sciences and Engineering Research Council of Canada (NSERC) for funding this research.