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Kearl Oil Sands Mining: Challenging Unconventional Wisdom

Abstract

The Athabasca Oil Sands are located in northern Alberta, Canada and contain an estimated 168 billion barrels of recoverable bitumen, 34 billion of which are estimated to be recovered through oil sands mining operations (Alberta Energy). Commercial-scale mining of the oil sands began in 1967 with operations at Great Canadian Oil Sands (now Suncor Energy). There are currently seven operating oil sands mines located in Alberta, with Imperial Oil's Kearl project representing the most recent start-up with bitumen production commencing in April, 2013. All of the oil sands mines produce bitumen from the Lower Cretaceous McMurray Formation, which consists of a stacked sequence of heterolithic fluvial sediments that were deposited directly above sub-cropping middle and early upper Devonian carbonates and evaporites. Accurately predicting facies distributions within fluvial successions is challenging. Inadequate subsurface characterization is the most commonly cited explanation for production problems in oil sands mining projects. Forty-seven years of experience has led industry to an approach that relies on dense corehole drilling to collect sufficient data to build simple, layer-cake geologic models of the subsurface. Typical corehole spacing is in the order of 100 m, with infill drilling required in areas of higher complexity. This approach necessitates large-scale annual drill programs that increase cost, safety exposure, and require rigorous management of large volumes of data. At Kearl, Imperial Oil is challenging forty-seven years of unconventional wisdom and is attempting to apply a fit-for-purpose data acquisition plan tailored to the Kearl ore body. The approach involves integrating industry learnings (typically anecdotal), statistical analysis of mined out properties of other mines, process-based fluvial sedimentology, corehole data, 2D and 3D seismic data, ground-penetrating radar, airborne electromagnetics and more sophisticated geobody-based geologic models of the subsurface. Results to date are encouraging: corehole spacing in the start-up area is wider than industry standard at 125 m – 175 m with no measurable impact on bitumen production. Imperial Oil will continue to apply this approach as we mine into areas of increased geologic complexity, applying an appropriate data acquisition and modeling strategy to appropriately characterize uncertainty. Over the entire mine life, this approach offers the potential to avoid over-drilling in relatively simple areas while acquiring denser datasets in areas that genuinely require it. This optimized approach, driven by subsurface complexity should result in efficient use of operating capital throughout the mine life.