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Better Oil Sands Extraction
August 1, 2011 | 4 Comments
Both Al Fin and Brian Wang have featured N-Solv, a Canadian process development of extracting oil out of the Athabasca Oil Sands bitumen deposited in huge amounts in northwest Canada. While environmentalists will never be satisfied, for those with a reasoned view, the N-Solv process is going to raise environmental confidence, improve the economics and produce much more oil.
N-Solve is asserting the new process will increase extraction rates. Simply put, the amount of oil per disturbance on the surface will go up. The process uses far less energy for heat, reporting 80 – 95% less energy needed. The oil dissolved out is more valuable, needs less thinning diluent, which reduces the pumping power needed and delivers a better product to refineries. For many, the most interesting improvement is the very heavy components of bitumen and the undesirable chemicals are left in place.
N-Solv Advantage Graphic. Click image for the largest view.
What is the N-Solv process?
A heated solvent vapor is injected at moderate pressures into a gravity drainage chamber at the bottom of the reservoir. The vapor flows from the injection well to the colder perimeter of the chamber where it condenses, delivering its heat and fresh solvent directly to the bitumen interface. The N-Solv extraction temperature and pressure are very gentle compared to in situ steam processes. The use of solvent also preferentially extracts the valuable components in the bitumen while the problematic high molecular weight coke forming species (asphaltenes) are left behind. The condensed solvent and oil then drain by gravity to the bottom of the chamber and are recovered by a production well.
The process is done on site, or “in situ” such that no massive digging up of the whole surface down to the deposit and through the oil sand formation is needed. Nor is the whole formation of the bitumen, sand, rock, sulfur, and metals dug out. The surface is minimally disturbed, cutting way back on the costs to move all the material, and when complete – put it all back and restore the land.
Keep in mind that bitumen from the oil sands is very carbon rich and hydrogen poor. Asphaltenes have the lowest hydrogen content – leaving them behind is highly beneficial. The N-Solv solvent deasphalting is very selective and leaves the asphaltenes evenly dispersed throughout the extracted portion of the chamber. Post extraction core analyses show that the residue contains 60 to 70% asphaltenes. By leaving the majority of the asphaltenes behind the produced oil contains less sulfur, heavy metals (zinc, vanadium, iron) and carbon residue. This partially upgrades the oil to 13-16°API from a value of approximately 8°API of raw bitumen. The produced oil is also less viscous, needs less diluent for pipeline transportation to the refinery.
The problem, which is worked out, is the undesirable impact of the non-condensable gases on the extraction rates. Non-condensable gases are released from the bitumen during the process and accumulate in the reservoir if no special measures are taken. Increasing concentrations of the non-condensable gases slows down the production rates. The effect can be severe and must be controlled. The right circulation of solvent in the N-Solv process provides sufficient capacity to minimize and stabilize the concentration of the non-condensables inside the reservoir. Through this built-in principle the process is able to sustain high production rates until the reservoir is fully drained.
The energy needed compared to dry steam is substantial, and the water for steam isn’t needed, making for a much less expensive process. In Athabasca bitumen, a 25-30º C temperature rise typically reduces the bitumen viscosity by a factor of 100. This promotes a substantial acceleration in the bitumen extraction rate with a very modest increase in temperature. That’s the key principle of N-Solv.
To achieve the desired temperature rise, it is necessary to have a solvent purity specification, as the condensation temperature is reduced by about 5ºC for every mole percent of methane contamination. Thus, even a small amount of methane contamination in the gravity drainage chamber can greatly impair the ability of the solvent to deliver heat to the bitumen interface. Methane is naturally present in the in situ bitumen, the use of high purity condensing solvent at moderate temperatures provides a very efficient mechanism to remove the in situ methane from the chamber. Thermodynamic calculations show that N-Solv will be perhaps 20 times more efficient at removing the non-condensable gas from the chamber than steam extraction processes.
Instead of burning huge amounts of methane, or natural gas, the N-Solv process should allow methane sales instead.
The question remains, what becomes of the solvent? N-Solv is reporting two primary recovery points, from the produced product, which can be reused, and recovery from the reservoir that can be recycled. The reservoir can hold quite a lot of solvent, but the price quoted for solvent on the N-Solv site is only $12 Canadian. This still makes recovery from the reservoir an economically viable effort. The N-Solv site has materials discussing the economics of recovery.
So, what is the solvent? No one is saying, it’s proprietary, obviously. It’s a secret that won’t last long as the demand will rise for understanding what’s left behind when a reservoir is finally abandoned.
It looks like the Canadians are on their way to a big improvement in the environmental effects of oil extraction from the oil sands with a big increase in production. Here’s hoping they can improve the profitability along the way. It’s been a decades old path to prosperity and the Canadians deserve a payoff for all the diligence and innovation to get to economic scale and serve the North American market.
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I can just see it now: GasLand 2 – It Came from the Oil Sands!
Thanks for you interest. I’ll just add a few more details. The solvent depends on the desired operating pressure and termperature. Propane is expected to have the best characteristics, but for shallower pay zones butane will be the preferred choice. In the reservoir, we replace bitumen liquid with mostly solvent vapour, so the solvent cost is comparable to the fuel cost in SAGD. However, the N-Solv plant is about half the cost of a SAGD plant. Furthermore by deasphalting the bitumen the oil production doesn’t require a coker and doesn’t suffer the 20% shrinkage from coke rejection. So the plant costs half as much as SAGD and the product is worth 25% more than SAGD and the opex are comparable to SAGD. According to Alberta Innovates, there are 600 billion barrels of stranded bitumen resource with a zero recovery factor that is too deep for mining and too shallow for SAGD.
[…] Better Oil Sands Extraction | New Energy and Fuel Canada's N-Solv has developed a much more environmentally friendly and energy efficient way to extract the oil from the controversial Athabasca Oil Sands.https://newenergyandfuel.com/ht .. […]
Hi,
Thanks for sharing such a valuable information.
It helps me in knowing N-Solv Process, in a better way.
Regards,
Prasanna
India