Oil sands, also called tar sands, are deposits of bitumen mixed with sand, clay, water, and/or stone. They exist worldwide; the largest deposits are in Canada and Venezuela. They represent millions of years of solar energy gathered by plants very much like the ones we know today. Humans extract them and refine them into crude oil for sale, using quixotically labor- and energy-intensive processes. This is evidence of the changing relationship between how fast humans use oil and how fast humans can get oil.
Bitumen is a miserable substance to interact with (imagine crude oil as a solid). You don't want it on
your skin; it doesn't come off easily, and the smell lingers.
Neanderthals dug up and burned bitumen forty thousand years ago. It was stuck to their stone tools, unearthed in Syria. The relationship between bitumen and homo sapiens is similarly old: bitumen was, at different places in the unrecorded world, waterproofing, adhesive, and building material. Seepages exist all along the Tigris and Euphrates rivers; Ancient Egyptians used bitumen as a sealant when preparing mummies.
First Nations people in Canada have, since time immemorial, used bitumen retrieved along the Athabasca and Clearwater rivers to waterproof their canoes, built with birch bark. Canadian oil sands deposits entered Western consciousness in 1719, when a Cree presented a sample to Hudsons Bay Company at Fort York. Six decades later Alexander Mackenzie would write about seepages he encountered near the fork of the same rivers, noting a depth of twenty-five feet.
Attempts to commoditize oil sands' energy met with problems, mainly physics. In 1939, L. C. Drummons, Secretary-Manager of the Alberta and North-West Chamber of Mines, wrote in The Pre-Cambrian:
"The tar sands, or more properly the oil sands, of the McMurray area
constitute probably the largest potential oil field in the world, and it
has been the dream of many oil technologists to find an efficient and
economic process of separating the oil from the sand in such a condition
that it will be readily processed in a modern refinery into gasoline,
diesel and fuel oil, and road oils. The engineers of Abasand Oils Ltd.,
at Fort McMurray, have for some time grappled with the problem and have
worked out a treatment which appears efficient and economical . . . It
is expected that trial runs will be made before the end of the year and
that the plant will be in full operation early in 1940."
Efforts at profitably extracting and refining bituminous sands continue to be herculean.
Extraction & Refinement
Near-surface oil sands are mined, much like ore. Deposits are often veneered with such troublesome things as forests and plains.
Nearly all oil sands producers employ some variant of the Clark Hot Water Extraction Method, developed by Karl Clark in the 1920s, to separate bitumen from embedded substrate. CTWEM applies to surface-mined oil sands, which represent 20% of known deposits. The process starts when chunks of bitumen etc. are crushed, then mixed with near-boiling water. The mix is then flowed at low speed over staggered, shaking plates to facilitate bitumen separation.
The stuff that sinks to the bottom goes to tailings pond
s (see problems, environmental). The water/oil mix is collected and shot from below with air
; the bitumen clings to the bubbles and floats to the top, becoming a substance known as "bitumen froth." This is de-aerated (you have accomplished
this very thing with soap bubbles if you have ever blown on them); the resultant, de-aerated bitumen froth is a mix of crude oil and less water and less solids than before. The froth is then mixed with various hydrocarbons and centrifuged a number of times in a process known as froth treatment. Rejected materials, again, go to tailings ponds.
Most oil sands are pumped, much like conventional oil. Because oil sands are solid at room temperature, possess a higher specific gravity than water, and are often laced with such metals as vanadium and nickel, they must be heated underground and injected with other hydrocarbons before being pumped and refined into crude oil using the aforementioned froth treatment processes.
Nearly all other, "cutting-edge" oil sands refinement processes involve more sophisticated applications of steam/chemicals. U.S. Oil is different, in that it uses chemicals derived from citrus.
Note that crude oil != gasoline. There exist several grades of crude oil, not to be explored here; gasoline, used primarily in the US, is refined from the highest grade of crude, while diesel is refined from middle-grade.
These can be filed under four headings: a) destruction of ecosystems by mining operations and tailings ponds; b) damage to ecosystems by broken pipelines; c) energy required to retrieve energy from oil sands; d) much-accelerated CO2 emissions.
Surface oil sands mining efforts require the removal of incidental landscapes. Oil sands formations often run laterally, requiring the removal of much landscape. Alberta's oil sands mines reflect this.
"Tailings" refers to the effluent of any mining operation. Ghost towns in the American Southwest surrounded by dunes the color of sunflower pollen can, for example, be said to be surrounded by tailings. All oil sands refinement processes produce tailings in liquid form, which are stored for later figuring-out in large aboveground ponds. All mining operations discard orders of magnitude more than they keep, and there are tailings ponds that approach the horizon. Buying enough land to make more of them is a problem in the industry. Oil sands tailings consist primarily of water, gravel, hydrocarbons, metals, and other substances, like sulfur. They currently occupy 67 square miles of Canada.
The Keystone Pipeline System, owned by TransCanada, delivers oil from Alberta to refineries in Steele City, Nebraska; Wood River and Patoka, Illinois; and Houston and Port Aurthur, Texas, on the Gulf Coast. It bisects the United States. I'm comfortable saying that all pipes carrying anything but water, and even many of the ones carrying water, are failure-prone. This map, published June 2011 by the New York Times, displays the sites of toxic fluid spills and indicates their size. Guess which are the most frequent/biggest. Crude oil and carbon steel do not good bedfellows make, nor do abrasives and the insides of valves. Note that June 2011 was three years ago.
EROI stands for Energy Returned on Energy Invested. It is an indicator of whether or not an energy source is worthwhile; it is also, understand, arbitrary in some ways and blind in others. It is determined by technology, infrastructure, and industry prices (themselves often a reflection of embodied energy). All energy sources are associated prominently with an EROI value. Hydroelectric power, for example, has an EROI value of 100; Coal is valued at 80; 1990 US oil imports at 35; 2005 US oil imports at 18; 2007 US oil imports at 12; tar sands at 3.
Oil Sands Today
2012 Oil Shale & Tar Sands Programmatic EIS