The chemical composition of the aqueous phase in oil sand slurries influences bitumen recovery from oil sands, especially those containing greater than 10% fines. The composition is controlled by a combination of mixing and dilution, ion exchange with clay surfaces and precipitation of divalent ions as carbonate minerals. Elevated levels of soluble potassium in the oil sand, which appear to be a marker for degraded illite or smectitic clays, are associated with depressed bitumen recovery. These clays have a swelling character and can contribute divalent ions to the slurry by ion exchange between the clay mineral surfaces and the process water.

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.