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Geotechnical News • December 2012
www.geotechnicalnews.com
WASTE GEOTECHNICS
The oil sands tailings
consortium
A “coalition of the willing” came
together in May of 2010 with an
overall objective to jointly develop
technologies that would reclaim oil
sands tailings ponds more rapidly.
The coalition used a “principle-based”
approach to put an agreement together
to create the Oil Sand Tailings Con-
sortium (OSTC). By December 2010,
the OSTC was announced with the
official agreement signed March in
2011. All of the companies currently
engaged in or considering surface
mining of the oil sands are members
of OSTC, including: Suncor Energy
Inc., Syncrude Canada Ltd., Shell
Canada, Canadian Natural Resources
Ltd., Imperial Oil, Total E & P Canada
Ltd. and Teck Resources Ltd. Vari-
ous collaborative projects have been
undertaken since the early 2000’s.
However, none of them were of the
magnitude of the commitment envis-
aged by the current OSTC Agreement.
The core of the OSTC Agreement is
founded on four principles: Eliminate
monetary and intellectual property (IP)
barriers; Share knowledge and sup-
port public transparency; Collaborate
on tailings R&D; and Equitable cost
sharing.
Under the OSTC Agreement, partici-
pating companies have agreed to share
all past, present and future tailings
technology IP. True collaboration, as
employed by the OSTC members, is
not a common industry practice and
this decision is a significant departure
from the typical oil and gas industry
practice. It required the more estab-
lished companies (Suncor, Syncrude
and Shell) who possess the major-
ity of the industries’ tailings IP and
have collectively invested over $400
million over the 5 years leading up to
the creation of the OSTC, to endorse
the arrangement. Participation from
all seven companies required a lower
threshold dollar amount that the newer
companies would contribute in order
to support future tailings R & D.
Under the OSTC
Agreement,
companies have
agreed to share all
past, present and
future tailings
technologies...
Tailings technical guide for fluid
tailings management
In support of improving the gover-
nance of oil sand tailings, the OSTC
set out technical guidelines for man-
aging FFT. This document entitled
“Tailings Technical Guide for Fluid
Tailings Management” was developed
with oversight and guidance provided
by two expert panels. The first panel
was convened to review the technical
content of the document. The panel
members were David Carrier III, Rich-
ard Dawson, Ross Eccles, Norbert
Morgenstern and John Sobkowicz. A
second panel reviewed the document
from a regulatory perspective. The
panel members were Richard Daw-
son, Gerry DeSorcy, John Errington,
Barry Hurndall, Bernie Roth and John
Sobkowicz.
The Technical Guide is intended to
support the Government of Alberta
in developing a consistent policy for
tailings regulation. It also provides a
detailed up-to-date technical review of
current practice for managing the dif-
ferent types of tailings deposits using
best available technology. Of most
importance, the document proposes
that site-specific volume profiles of
FFT be established for each mine
site. This approach provides a direct
method to manage and steward the
volume of FFT. Furthermore, it will
limit the accumulation and provide
containment of FFT in a manner
consistent with the goals of progres-
sive reclamation as well as the desired
reclamation and closure outcomes.
Under this proposal, oil sand opera-
tors would employ adaptive manage-
ment to remain within their committed
volumes. Adaptive management deals
with inherent uncertainties associated
with FFT generation, allowing opera-
tors to deploy available methods (and
newly developed ones like those iden-
tified in the Tailings Roadmap Study)
as required. Different technologies are
available that form combined suites to
meet various performance objectives
within the overall tailings plan for a
project.
Oil sand tailings processing and
deposition
Various process methods are currently
being utilized to release water from
FFT. The FFT must attain a solids
content of 75% to 80% (by weight) to
develop sufficient long-term stiffness
and strength (in the range of 50 kPa
to 100 kPa), thus losing 67% to 75%
of its water in the process. For tail-
ings treatment technologies involving
drying, FFT might further dewater as
far as the shrinkage limit. At pres-
ent there are five primary techniques
being evaluated for dewatering of
FFT. These include: i) Centrifugation
of FFT, ii) Thin Lift Dewatering, iii)
Thick Lift Dewatering, iv) Thickened
Tailings, and v) CT or NST Tailings.
Each of these are described below.
One process to dewater FFT uses
flocculation and processing of FFT
through a solid-bowl scroll centrifuge.
Adding a coagulant such as gypsum
can also assist the process. Solids
contents of about 55% are produced
in the centrifuge “cake.” The cake
is placed in relatively thin lifts with
about 2 t/m2-y deposited in cells
constructed in a manner similar to
the handling of soft, wet overburden
soils. Left for a winter freeze-thaw
cycle, the cake will attain peak shear
strengths of 5 kPa to 10 kPa, before an
additional lift is placed. Alternatively,
the cake is continuously deposited, at