A few hundred millions years ago, Earth had many shallow seas. Blue-green algae flourished in their warm waters fuelled by solar energy.
Other creatures grazed on these algae, munching their carbohydrate, fat and protein to power themselves, much as sheep and cattle graze on grass. Grazers and the predators which ate them were tiny, single-cell animals and also larger ones like shrimp. (Fish did not yet exist.)
Over thousands of years, these animals lived, multiplied and died, creating thick deposits of organic material at the bottom of these seas. Atmospheric dust and water-borne sediment mixed with the organics, eventually burying everything to a depth of several kilometres.
Under great pressure, caused by the weight of material above, and high temperature, at that depth, the buried gradually consolidated into sedimentary rock – rock with distinct layers, each corresponding to the material it formed from.
Meanwhile, the buried organics were decomposing, losing carbon dioxide, water, methane, and other organics like propane, leaving behind an oily liquid within a porous rocky reservoir.
This oily material could stay where it formed, or migrate to neighbouring layers of rock, if these were porous.
In places, movements of the Earth’s crust caused the rock layers to bend and buckle. Occasionally, they formed domes where the oily material could accumulate.
If these oily accumulations were covered by impermeable rock, the organics remained trapped, to be discovered by 20th-century petroleum hunters.
Typically, the oily material in its porous rock reservoir is sandwiched between water below and natural gas above. The salty water is a remnant of the sea in which the organic material formed, plus water lost during decomposition.
As the organic material decomposes, methane and propane gas — plus other minor hydrocarbon gases — tries to escape, but the impermeable cap rock keeps them in the reservoir. In some places, geological movement and erosion exposes edges of a petroleum reservoir allowing oily material to ooze out. This was used by the ancients to waterproof roofing and boats, or to glue together bricks. Some Baghdad streets were paved with it.
They called the material petroleum or “rock oil” from the Greek petra (equals 'rock') and elaion (equals 'oleum' or 'oil'). Drilling into a “conventional” oil reservoir, the petroleum is often under great pressure, and pushes itself to the surface on its own. As petroleum is extracted, pressure drops. Further extraction may require mechanical pumping. The owners decide if enough material remains to justify the investment. They must also guess future world oil pricing.
As the petroleum comes to the surface, dissolved gases bubble off, just like those forming when beer or soda pop is opened. These are what we call “natural gas” plus CO2. Its composition is roughly 80 per cent to 90 per cent methane and 10 per cent to 20 per cent propane with small amounts of butane, ethane and other gaseous hydrocarbons.
Refineries remove everything but methane, which is sent to us by pipeline to heat buildings and for industrial purposes. The other hydrocarbons are sold separately: propane in portable tanks, butane in small disposable lighters, while ethane goes to make plastics like polyethylene.
Large amounts of bitumen-impregnated sand are found in north-eastern Alberta. Although this huge deposit began in the same way as the conventional oil deposit described above, it was not buried deeply enough to create the pressure required to consolidate the sand into rock. No impermeable layer formed above the sand.
In the absence of an impermeable rock cap, hydrocarbon gases seeped out of the reservoir.
Low boiling-point liquids such as pentane, hexane and octane also escaped, leaving behind the semi-solid, tar-like bitumen.
Originally labelled “tar sands,” the name was sanitized to “oil sands.” Material near the surface, is strip-mined and transporting to a facility where it is heated to melt the bitumen and separate it from the sand.
Bitumen is obtained from deeper deposits by injecting high-temperature steam. The bitumen melts, flowing down a previously made channel to a collection point.
Alberta’s deposits are roughly 85 per cent sand, 10 per cent bitumen and five per cent water. The high sand content means a great deal of heat must be applied to achieve separation, creating elevated carbon emissions. Averaging competing claims, about 20 per cent more energy is needed to win this unconventional petroleum, but it’s not yet petroleum.
The bitumen must be “upgraded” by “cracking” the long, tarry molecules into shorter oily ones to form synthetic crude oil.
Some 20 tonnes of tar sands must be processed to yield one tonne of synthetic crude. Unfortunately, the mining process, extracting bitumen from the sand and making the synthetic crude, requires a lot of water, which becomes contaminated. This water is kept in 'tailings ponds' while engineers work out methods to clean it
up enough to return it to the Athabaska River.
According to their agreement with the Alberta government, tar sands miners are required to restore the disturbed land to its original state. This work is well behind schedule. Environmental groups and First Nations people worry it may never be completed.
And, they have ample reason to be concerned. Many producers of conventional oil and gas slipped away, leaving behind thousands of played-out properties whose wells have never been properly sealed.
Environmental groups (full disclosure: I consider myself an environmentalist) campaign against exploitation of the tar sands for the above reasons. They also claim that marketing of Canadian petroleum contributes to continued consumption and associated carbon emissions.
However, their suggestion that Canadian petroleum production somehow increases the world’s burning of liquid fuels prolonging “the age of oil” is unlikely to be true. Whether a Ghanaian, Indonesian or American decides to buy and drive a vehicle with an internal combustion engine doesn’t depend on Canada. Their decision-making take little, if any, note of environmental matters.
New car showrooms in North America and Europe will be filled with electric cars within a decade. That will put a serious crimp into the demand for gasoline and lubricants.
I would argue that the petroleum Canada produces displaces oil which would otherwise come from Russia or Saudi Arabia. Russia uses oil revenue to wage war on its neighbour, Ukraine. This war produces far greater carbon emissions than tar sands mining in Canada! Saudi Arabia uses its oil wealth to suppress women and to wage war on Yemen! Iran used its petroleum revenues to build nuclear weapons.
Many oil producers, such as Venezuela, Angola and Algeria, have unsavoury governments which keep themselves in office with military power.
Canada’s tar sands petroleum is not carbon-free, but its production is fairly ethical. Until the world weans itself off oil, Canada should continue production, reducing the market share available for these competitors.
Peter Bursztyn is a self-proclaimed “recovering scientist” who has a passion for all things based in science and the environment. The now-retired former university academic has taught and carried out research at universities in Africa, Britain and Canada. As a member of BarrieToday's community advisory board, he also writes a semi-regular column. If you have a question Peter might be able to answer or something you're curious about, email us at [email protected].
