Thermal
In-Situ Thermal
Canada's oil sands deposits are estimated to contain 1.7 to 2.5 trillion barrels of oil in place, more than known reserves of the Middle East. This oil is in the form of bitumen, which in its natural state, is too viscous to flow. When bitumen is too deep (>80 m) to economically mine, steam is injected, reducing the oil viscosity and allowing it to be pumped through surface wells. Only about 7% of Canada's oil sands can be mined, the majority has to be recovered using thermal in-situ recovery.
Canadian Natural is the 2nd largest thermal producer in Canada with a current production of approximately 45,000 bbl/d, an increase of over 18% from 2003 levels. Currently the favored in-situ thermal recovery schemes are Steam Assisted Gravity Drainage (SAGD) and Cyclic Steam Stimulation (CSS).
Steam Assisted Gravity Drainage (SAGD)
Canadian Natural is an industry leader, successfully implementing one of the first SAGD programs in Canada at our Wolf Lake property. SAGD wells are drilled in pairs and use continuous steam injection to mobilize bitumen. As the figure below illustrates, steam is injected into the upper well mobilizing bitumen above it and causing it to drain under the pull of gravity to the lower production well.
Advantages:
Disadvantages:
SAGD will be the preferred production process for the McMurray Formation at Canadian Natural's Horizon and Gregoire fields.
Cyclic Steam Stimulation (CSS)
Canadian Natural also employs cyclic steam or "huff and puff" technology to develop bitumen resources. This technology requires one well bore and the production consists of two distinct phases:
1. Injection - Steam is injected for several weeks, mobilizing cold bitumen.
2. Production - Flow on the injection well is reversed producing oil through the same injection well bore.
These two phases together comprise one cycle. Steam is re-injected to begin a new cycle when oil production rates fall below a critical threshold due to the cooling of the reservoir.
Canadian Natural is a leader in the commercial application of horizontal well CSS illustrated in the figure below.
Advantages:
Robust, proven technology
Requires 1 well bore (reduced capital investment)
Adaptable to thinner inter-bedded reservoirs
Disadvantages:
CSS is the preferred production process in the Clearwater Formation at Canadian Natural's Wolf Lake, and Primrose (North, South, and East) fields.
Primrose/Wolf Lake and Other In-situ Operations
The Primrose/Wolf Lake Oil Sands Project is a thermal in-situ operation located approximately 55 km north of Bonnyville in northeastern Alberta. Both cyclic and SAGD technologies are currently employed to produce approximately 80,000 barrels of oil per day. We plan to expand our Primrose and Wolf Lake In-situ Oil Sands operations to more than 120,000 barrels of oil per day. Canadian Natural is currently preparing a proposed development plan for Kirby In-situ Oil Sands Project.
We also have in-situ opportunities on the western edge of our synthetic crude oil mine site, the Horizon Oil Sands Project.
