Canada's Oil Sands (Part Two)

The September Resource of the Month focused on the history of Alberta's oil sand's and the McMurray formation which is the source of Alberta bitumen October will focus on the various modes of bitumen recovery and processing. The recovery and refining process is all together quite simple but the mechanical and colossal machining aspects are what classify the various projects as marvels in engineering The Bucket-Wheel (Figure 1) and Dragline (Figure 2) were the first terms in oil sand's recovery that were added to my vocabulary When I was first introduced to those terms I had never actually made my way north to see the layout of the mines.

Oil saturated sand and some bulldozers didn't exactly interest me until I had two more years under my belt and that much more knowledge to realize and understand the significance of the oil sands. The equipment used to recover the bitumen is rather amazing in that they are often compared in size to small downtown office towers and capable of moving massive amounts of material in a short amount of time (Figure 3).

There are essentially two components involved in the transporting of bitumen to the first stage of processing, the shovels and dump truck's The bucket-wheel and dragline were the first generation of shovels used to mine the oil sands The bucketwheel was a mammoth cumbersome tool, which resembled a giant miter saw The bitumen would be scooped up by the numerous buckets at the end of the wheel and tossed onto an awkward network of conveyor belts to be processed.

Today the bucketwheel is no longer used for mining They have all either been dismantled or stand as reminders in museums of the early days in oil sand mining The dragline replaced the bucketwheel but it too is a clumsy machine which is very expensive to operate and rather inefficient Today the dragline like the bucketwheel is also being phased out and replaced by hydraulic shovels (Figure 4) which are flexible, efficient and economical With the onset of the dragline came the giant dump trucks, capable today of carrying up to 380 tones per load (Figure 4) The trucks like the dragline, bucketwheel and hydraulic shovels follow a similar tradition in that they are so large they have to be transported to the mine in sections and assembled on site.

Once the bitumen is recovered it is hauled by dump truck to hoppers which break up clumps and removes cobbles and boulders (Figure 5) Conveyor belts typically moved the oil sands to the processing plant but today the belts have been replaced by a transport method called hydrotransport Hydrotransport works by flooding the bitumen after it has been through the hoppers with hot water The hot water lowers the viscosity of the bitumen and allows it to flow out of the sand and to the top of the slurry This slurry is transported by pipeline to the plant for further processing.

At the processing plant the slurry falls into a separation vessel where the sand (tailings), water and oil are separated The sand is then sent back to the mine site and stored to later fill in the mined out areas The water is recycled and used over and over in the same process The bitumen is skimmed from the water and sent to the upgrader.The upgrader converts bitumen and heavy oil into a product with a density and viscosity comparable to light crude oil This is accomplished in a two-stage process In the first stage coking or hydrocracking is used to break down the bitumen molecules Coking removes carbon, while hydrocracking adds hydrogen In the second stage hydrotreating is used to stabilize the product and to remove impurities such as sulphur which is recovered and used for fertilizer and other means From upgrading comes three main products: naphtha, kerosene and gas oil These three fluids can be blended to make a crude oil equivalent or sold and used separately.

In-Situ Bitumen Athabasca, Peace River, and Cold Lake Cyclic Steam Stimulation If bitumen is too deep to recover using open pit methods it can be heated, diluted and recovered using conventional rig operations The first stage in recovery is the drilling of a hole in the bitumen zone Steam is then injected into the well and into the bitumen, this reduces the viscosity of the bitumen and allows it to flow The third step involves a waiting period where the bitumen is allowed to soak In the final phase production begins and the bitumen is pumped to surface Once production rates begin to decreases the steam-soak cycle begins again.

Steam Assisted Gravity Drainage Two horizontal wells are drilled one on top of the other (Figure 6) Steam is injected into the upper well, this reduces the viscosity of the bitumen and allows it to flow downward by gravity The bitumen is then brought to surface by the lower horizontal well. Current in situ methods recover between 25 and 75 per cent bitumen which is better than most conventional light crude wells.

Conclusion Athabasca, Peace River, and Cold Lake Production of oil sands and heavy oil is dependent on two factors: the cost of production and transport to markets and the price buyers are willing to pay Prices are determined by supply, demand, world politics, and many other factors Since prices are difficult to foresee it is of the producers best interest to lower their production cost by continuously improving technology and imaginative techniques for bitumen recovery.