My Science School

The rocks in which deposits of crude (unrefined) oil are found may be hundreds of meters beneath the soil or the sea bed. In either case, a shaft must be drilled down to the deposits. On land, the drill can be set up on a steel structure called a derrick. At sea, a drilling platform is needed. This may have legs that stand on the sea bed or, in very deep water; the drilling platform may float on the surface. Floating platforms must still be anchored firmly to the sea bed so that they can withstand high winds and tempestuous seas.

Conventional oil is extracted from underground reservoirs using traditional drilling and pumping methods. Conventional oil is a liquid at atmospheric temperature and pressure, so it can flow through a wellbore and a pipeline – unlike bitumen (oil sands oil) which is too thick to flow without being heated or diluted. It’s easier and less expensive to recover conventional oil and it requires less processing after extraction. Conventional oil development is both land-based and offshore.

Unconventional oil cannot be recovered using conventional drilling and pumping methods. Advanced extraction techniques, such as oil sands mining and in situ development, are used to recover heavier oil that does not flow on its own. Oil found in geological formations that make it more difficult to extract, such as light tight oil (LTO), is also called unconventional oil because non-traditional techniques are needed to extract the oil from the underground reservoir. Light tight oil is found throughout much of the Western Canadian Sedimentary Basin (WCSB), plus in Central and Eastern Canada. LTO is found deep below the earth’s surface, primarily within low-permeability rock formations including shale, sandstone and mudstone reservoirs. This kind of oil extraction uses horizontal drilling and hydraulic fracturing.

The Canadian regions with tight oil reservoirs include the Bakken, which is found primarily in Saskatchewan; several fields in Alberta including Cardium and Viking; and the Montney and Duvernay in Alberta and B.C.

Surface mining is used when oil sands deposits lie within 70 meters (200 feet) of the earth’s surface. Twenty per cent of oil sands reserves are close enough to the surface to be mined. Large shovels scoop oil sand into haul trucks that transport it to crushers where large clumps are broken down. The oil sand is then mixed with hot water and pumped by pipeline to a plant called an upgraded, where the bitumen (oil) is separated from the other components such as sand, clay and water.

Tailings ponds are common in all types of surface mining around the world. In the oil sands, tailings – consisting of water, sand, clay and trace amounts of oil – are pumped to ponds where the sand and clay gradually settle to the bottom. Water near the top is reused in the mining and bitumen separation process.

Once a tailings pond is no longer needed, it is reclaimed. Oil sands companies that have mining operations are researching many techniques to solidify the tailings faster so the ponds can be dried out, re-surfaced with soil, and planted with local tree and shrub species.

Picture Credit : Google