The extremely high
viscosity at Wabasca has necessitated extreme production methodsi
including water, steam and polymer injection, steam assisted gravity
drainage (SAGD), and Solvent Aided Processing (SAP). All of these
production processes have released some of the most toxic hydrocarbon
compounds from the bitumen and have added additional toxic chemicals
(like surfactants) into the heavy oil.
Surfactants
are added to make oil more slippery and thus improve recovery
percentage. The chart below shows the toxicity of some non-ionic
surfactantsii
which may be used in oil fields to form emulsions with less foam.
Figure
6
Toxicity Comparisons of Surfactants
SOURCE: Env.
Tox. II 2008 pg, 286
Those surfactants at the top of the
chart with an EC 50 (concentration at which 50% of test organisms
die) of less than 10mg/L are classified as toxic to aquatic life and
those between 10 and 100 mg/L are merely considered harmful.
Although the specific surfactants used in polymer floods
in Alberta are usually not named, (proprietary secrets) Triton X and
the Tween series have frequently been associated with surfactants in
polymer flood operations in other areas.
No comments:
Post a Comment