Heavy
crude oil and bitumen are characterized by a low yield of
light distillates in the range of 10–30% with a boiling point
below 350 °C, high density (low API gravity), high viscosity,
and high heteroatom content, which impede their exploitation. In this
study, the catalytic upgrading process in situ (developed by the Petroleum
Recovery Institute, Canada) add-on to the toe-to-heel air injection
for the extraction and upgrading of heavy oil and bitumen downhole
was investigated. The effect of steam addition and steam-to-oil ratio
upon upgrading, coke formation, sulfur and metal removal were examined
using a Co–Mo/γAl2O3 catalyst at
a reaction temperature of 425 °C, pressure of 20 bar, gas-to-oil
ratio of 500 mL·mL–1, and steam-to-oil ratio
in the range of 0.02–0.1 mL·mL–1. It
was observed that the coke content of the spent catalyst reduced from
17.02 to 11.3 wt % as the steam-to-oil ratio increased from 0.02 to
0.1 mL·mL–1 compared to 27.53 wt % obtained
with only nitrogen atmosphere after 15 h time-on-stream. Over the
same range of conditions, 88–92% viscosity reduction was obtained
as steam-to-oil ratio increased compared to 85.5% in nitrogen atmosphere
only, a substantial reduction from the value of 1.091 Pa·s for
the feed oil. It was also found that although desulfurization increased
from 3.4% in a steam-free atmosphere to 16–25.6% over the increasing
range of steam flows investigated, demetallization increased from
16.8% in a steam-free environment to 43–70.5% depending on
the increasing steam-to-oil ratio.