Bitumen contained in ore bodies (oil sands) is recovered using either surface mining with subsequent physical/mechanical recovery unit operations or with an in situ recovery process referred to as Steam assisted gravity drainage (SAGD). About 80-85% of the total oil sands reserves employ the SAGD process. In the SAGD process, steam generated at a centralized boiler house using once through steam generators (OTSG) is transported to oil wells located at distances anywhere between 2 and 10 km. The steam pressure at the OTSG is 10 MPa, while at the inlet of the well it is 4 MPa and inside the well it is 2.5 MPa. The water-oil emulsion recovered from the oil well is then pumped to the central processing facility. Oil and water are separated from this emulsion using knock-out drums. Since environmental regulations require a high recycle ratio of water, the dirty water is re-used using a series of water cleaning unit operations before it can be used as boiler feed water for the OTSGs.
The existing water recovery/steam generation process has drawbacks and limitations that include, but are not limited to, high capital costs, long installation and commissioning times, long start-up and shutdown times and low process availability. The current process is also not economically viable for smaller or isolated well pads.
USPTO Backgrounds
USPTO Backgrounds