The Athabasca oil sands in Alberta, Canada are one of the largest oil reserves in the world [Hum08]. However, 80% of the oil sands are too deep for mining and require in-situ extraction methods, such as Steam Assisted Gravity Drainage (SAGD) to bring the heavy oil, or bitumen, to the surface. Much work is required before producing of the heavy oil can begin, including identifying an exploration region, gaining approval for development, and constructing the necessary infrastructure. This case study investigates how EM can be used in the initial stages of exploration at a site in the oil sands.
The area of focus is the Aspen property, which is owned by Imperial Oil, and is the future site of several SAGD well pads. The project area lies about 45 km northeast of Fort McMurray and 25 km southeast of Fort McKay in northeastern Alberta, Canada. Fig. 302 shows the Aspen property in relation to the two towns and the other properties in the area.
The geology at the Aspen property contains the following flat-lying layers [Ken13]:
- The Quaternary consists of paleo-channels and glacial tills. Its thickness varies between 60 and 100 m.
- The Grand Rapids Formation is a transgressional layer consisting of shales and sands, and can be incised by the overlying Quaternary channels. Its thickness varies between 30 and 110 m.
- The Clearwater Formation consists of shales and acts as a cap rock for SAGD operations. The Wabiskaw Member is a transgressional layer containing sands and shales at the base of the Clearwater. The Clearwater is 65-90 m thick while the Wabiskaw Member is approximately 5 m thick.
- The McMurray Formation is the main oil sands reservoir with a thickness of 45-115 m.
- A Devonian limestone unit is separated from the McMurray Formation by an unconformity. Prairie Evaporites may exist along the unconformity, either as salt or salt dissolution [Bro13].
As these units differ in composition, their electrical resistivity (or conversely, conductivity) differ as well. The next page discusses the Properties in detail.