Development of Composite Tailings Technology at Syncrude

During extraction of bitumen from the Athabasca Oil Sands, an aqueous fines suspension, called mature fine tails (MFT), is produced. The geotechnical characteristics of MFT demand long term storage in geotechnically secure containment areas. The composite tailings (CT) process involves mixing a coarse tailings stream with a MFT stream and adding a coagulant to form slurry that rapidly releases water when deposited and binds the MFT in a coarse tailings/MFT deposit. Thus, more of the fines can be stored in a geotechnical soil matrix, which reduces the inventory of fluid-fine tails and enables a wider range of reclamation alternatives. CT process optimization, coupled with public and regulatory consultation at key milestones, has led to a corporate commitment to implement this technology. This paper reviews key aspects of the evolution of the CT process at Syncrude, including segregation, depositional and geotechnical characteristics of CT mixes that are formed with various chemical aids. Some of the treatments discussed include those based on the use of acid, lime, gypsum, alum, and organic polymers as the coagulant aids.