BITUMEN CHEMICAL-CHANGES DURING AQUATHERMOLYTIC TREATMENTS OF COLD LAKE TAR SANDS

Cold Lake tar sand samples have been treated in the laboratory in neut ral water and caustic brine at 250 +/- 3 degrees C for up to 75 days t o simulate the environment during the steam-displacement process used to recover heavy oil (bitumen) from subterranean reservoirs. Observed chemical changes in the isolated bitumen fractions include volatiles g eneration and asphaltene reduction, both of which affect the viscosity of the oil. Maximum volatiles levels, and minimum viscosities and asp haltene concentrations, were achieved in a 30 to 50 day time-frame. Lo nger term treatments showed a reversal of these changes. The generated volatiles from the 50 day treatments were isolated and determined to be mostly olefinic in nature. These olefins can then undergo proposed addition reactions that would be consistent with the changes observed for the properties of the whole bitumen.