ESL Lesson 1
Oil in Our Every Day Life
ESL Lesson 2
The History of Mining
ESL Lesson 3
Economic growth
ESL Lesson 4
Delivery Systems
ESL Lesson 5
Cities and Population Movement
ESL Lesson 6
Recycling
ESL Lesson 7
Rubber
ESL Lesson 8
Farming
Extraction Process
Surface Mining
For the last 38 years or so, bitumen has been extracted from the Athabasca Oil Sands by surface mining (strip mining). In these oil sands there are large deposits of bitumen with little top cover, making mining the most efficient method of extracting it. The top cover (overburden) consists of muskeg (peat bog) over top of clay and sand. The oil sands themselves are typically (usually) 40 to 60 meters deep, sitting on top of flat limestone rock. In recent years companies such as Syncrude and Suncor have switched (changed) to much cheaper shovel-and-truck operations using the biggest power shovels (100 tons) and dump trucks (400 tons) in the world. This has reduced production costs to around $15 per barrel of synthetic crude oil. After excavation (digging it up), hot water and caustic soda (NaOH) is added to the sand, and the resulting slurry (wet mixture) is piped (sent by pipe) to the extraction plant where it is agitated (shaken) and the oil skimmed (removed) from the top. It is essential (most important) that the water chemistry is appropriate (correct) to allow bitumen to separate from sand and clay, the combination of hot water and agitation (shaking) releases bitumen from the tar sand, and allows small air bubbles to attach to the bitumen droplets. **This is why they need so much clean water and where the problems of processing bitumen arise if the water source dries up or is not available** The bitumen froth floats to the top of separation vessels (tanks), and is further treated (again treated) to remove residual (extra) water and fine solids (tiny pieces of sand) Bitumen is much thicker than traditional crude oil, so it must be either mixed with lighter petroleum (either liquid or gas) or chemically split (broken down into smaller parts with other chemicals) before it can be transported by pipeline for upgrading into synthetic crude oil. Recent enhancements (improvements) to this method allow the extraction plants to recover over 90% of the bitumen in the sand. Three oil sands mines are currently in operation. The original Suncor mine opened in 1967, while the Syncrude mine (the biggest mine in the world) started in 1978 and Shell Canada opened its Muskeg River mine in 2003. New mines under construction include Shell Canada's Jackpine mine. Imperial Oil's Kearl Lake mine, Svnenco Energy's Northern Lights mine, and Petro-Canada's Fort Hills mine. It is estimated that around 80% of the Alberta tar sands and nearly all of Venezuelan sands are too far below the surface to use the open-pit mining technique used by the large producers. A number of in-situ techniques have been developed to extract this deeper oil. More info at: http://www.oilsandsdiscovery.com/oil_sands_story/insitu.htmlCold Flow or Cold Heavy Oil Production with Sand (CHOPS)
In this technique, the oil is simply pumped out of the sands, often using specialized pumps called progressive cavity pumps. This only works well in areas where the oil is fluid enough to pump. It is commonly used in Venezuela (where the extra-heavy oil is at 50 degrees Celsius), and also in the Wabasca, Alberta Oil Sands and the southern part of the Cold Lake. Alberta Oil Sands. It has the advantage of being cheap and the disadvantage that it recovers only 5-6% of the oil in place. Some years ago Canadian oil companies discovered that if they removed the sand filters from the wells and produced as much sand as possible with the oil, production rates improved remarkably. This technique became known as Cold Heavy Oil Production with Sand (CHOPS). Further research disclosed (showed) that pumping out sand opened "wormholes" in the sand formation which allowed more oil to reach the wellbore (well opening). The advantage of this method is better production rates and recovery (around 10%) and the disadvantage that disposing (get rid of) of the produced sand is a problem. A novel way to do this was spreading it on rural roads, which rural governments liked because the oily sand reduced dust and the oil companies did their road maintenance for them. In recent years disposing of sand in underground salt caverns has become common.
Cyclic Steam Stimulation (CSS)
The use of steam injection to recover heavy oil has been in use in the oil fields of California since the 1950's. The Cyclic Steam Stimulation or "huff-and-puff" method has been used since 1985. In this method, the well is put through cycles of steam injection, soak, and oil production. First steam is injected (forced) into a well at a temperature of 300 degrees Celsius for a period of weeks to months, then the well is allowed to sit for days to weeks to allow heat to soak into the formation (oil filled sands), and then the hot oil is pumped out of the well for a period of weeks or months. Once the production rate falls off (decreases), the well is put through another cycle of injection, soak and production. This process is repeated until the cost of injecting steam becomes higher than the money made from producing oil.(Becomes and energy sink) The CSS method has the advantage that recovery factors are around 20 to 25% of oil in place and the disadvantage that the cost to inject steam is high, as well the energy input to create the steam.
Steam Assisted Gravity Drainage (SAGD)
Steam assisted gravity drainage was developed in the 1980s by an Alberta government research center and coincided (happens at the same time) with improvements in directional drilling technology that made it quick and inexpensive to do by the mid 1990's. In SAGD, two horizontal (sideways) wells are drilled in the oil sands, one at the bottom of the formation and another about 5 meters above it. These wells are typically drilled in groups off central pads (areas) and can extend for miles/kilometers in all directions. In each well pair, steam is injected into the upper well, the heat melts the bitumen, which allows it to flow into the lower well, where it is pumped to the surface. SAGD has proved to be a major breakthrough in production technology since it is cheaper than CSS, allows very high oil production rates, and recovers up to 60% of the oil in place. Because of its very favorable (positive) economics and applicability (usability) to a vast area of oil sands, this method alone quadrupled (4X) North American oil reserves, and allowed Canada to move to second (2nd) place in world oil reserves after Saudi Arabia.
Vapor Extraction Process (VAPEX)
VAPEX is similar to SAGD but instead of steam, hydrocarbon solvents (chemicals made from oil) are injected into the upper well to dilute (make thinner) the bitumen and allow it to flow into the lower well. It has the advantage of much better energy efficiency than steam injection and it does some partial upgrading (changing) of bitumen to oil right in the formation (area of oil sands).
The above three methods are not mutually exclusive (used only by themselves). It is becoming common for wells to be put through one CSS injection-soak-production cycle to condition (get ready) the formation prior to going to SAGD production, and companies are experimenting with combining VAPEX with SAGD to improve recovery rates and lower energy costs.
Toe to Heel Air Injection (THAI)
This is a very new and experimental method that combines (mixes) a vertical air injection well with a horizontal production well. The process ignites (lights on fire) oil in the reservoir and creates a vertical (up and down) wall of fire moving from the "toe" (front) of the horizontal well toward the "heel" (back), which burns the heavier oil components (parts) and drives (pushes) the lighter components into the production well, where it is pumped out. In addition, the heat from the fire upgrades (changes) some of the heavy bitumen into lighter oil right in the formation. Historically fireflood projects have not worked out well because of difficulty in controlling the flame (fire) front and a propensity (thing that usually happens) to set the producing wells on fire. However, some oil companies feel the THAI method will be more controllable and practical, and have the advantage of not requiring energy to create steam. **I wonder how much smoke this releases? Discussion topic: Pollution emissions.
Continue to: Environmental Impacts
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Cities and Population Movement
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Possible Alternatives to Replace Crude Oil
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Extraction Process
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Environmental Impacts
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