Oil sands
Oil sand or tar sand is a mixture of various sand -grain-sized mineral grains (mainly quartz ) and water and depleted of volatiles oil. Depending on the viscosity and degree of depletion of this oil is a natural heavy oil (yet relatively liquid) or natural bitumen called (very tough or resistant). Oil sands in common is their storage in a relatively small depth (a few 100 m). They are often even directly at the surface. Sandstones, which are stored in greater depth and from which refining capable without special funding process, "light" crude oil can be recovered, are more likely to respond than because erdölhöffige or leading sandstones as oil sands.
The world's major oil sand deposits are located in Canada and Venezuela. At or very near the earth's surface located oil sands are mined in open pit mining. Out of the depths overlying oil sands bitumen or even relatively "light" crude oil with so-called in-situ methods (eg the injection of steam into the reservoir ) can be obtained. In Lower and the Upper Rhine oil sands were also degraded by mining underground.
With rising oil prices and technical progress, the production of synthetic crude oil from oil sands is always more profitable. The Government of Canada encourages the exploitation of oil sands and sees this as an important, secure the future economic factor.
- 3.1 opencast
- 3.2 In - situ processes
- 3.3 treatment 3.3.1 bitumen extraction
- 3.3.2 " Upgrading"
Origin and composition
General
It is assumed that oil sands in most cases that arise from a sandy, more or less consolidated sedimentary rock with a small proportion of primary organic carbon ascending from the depths of crude oil is impregnated. Herein lies an important difference to the oil shale, in which it is a rather fine-grained ( pelitisches ) potential petroleum source rocks with a high proportion of primary organic carbon. Most oil sands deposits are therefore nothing more than shallow oil reservoirs. By contact of the crude oil with oxygen and the loss of volatile, short-chain components, the original relatively low- oil has been transformed in a natural way in a viscous bitumen. The oil has migrated either directly from the parent rock up in near-surface sediments or from a primary reservoir below the oil sand deposit. Oil sands, therefore, are often found in areas where there are "real" oil deposits.
However, some oil sands could also be created directly from organic-rich, sandy sediments and therefore belonged to an independent form of hydrocarbon reservoirs.
The mineral fraction consists mainly of quartz, to lower levels for other minerals such as feldspar, mica, rutile, zircon, tourmaline, or hematite, and clay minerals, such as kaolinite. The hydrocarbon content in the sands is between one and 18%. Reduce oil sand with a hydrocarbon content of less than 6% is technically possible, but currently (as of 2007 ) uneconomical. On average, a barrel (159 liters) of crude oil is extracted from two tons of oil sands.
" Hydrophilicity " of oil sands
Some oil sands are in their composition as " hydrophilic" ( or English. Water -wet, wasserbenetzt ') respectively. The characterization as "hydrophilic" is misleading, since hydrophilicity is a property of the surface or on a smaller scale, of molecules. However, oil sand is a mixture of diverse materials whose surfaces or molecules are both hydrophilic and hydrophobic. Oil sands should therefore not be characterized by the term " hydrophilic". The more appropriate attribute in this case is "water - wet".
"Water - wet" means that the mineral grains are not directly in contact with bitumen, but are intended to be covered by a more or less closed, thin film of water. However, there is so far no direct evidence that actually exist between bitumen and mineral grains such water films. The hypothesis of the existence of such water films is confirmed with the fact that many clean mineral surfaces, including those who actually are hydrophilic quartz. Was the sediment body saturated with water before impregnation with oil, would remain due to the hydrophilicity of the quartz grains of water on the grain surfaces back. Also subsequently penetrated into the oil sand water would be due to the hydrophilicity of the quartz grains accumulate on those. The applicability of the hot water extraction is regarded as evidence that an oil sand "water - wet" is.
The opposite of "water - wet" is "oil - wet" ( wetted with oil, '). " Oil - wet" means that the grain surfaces "dry" or are directly related to the bitumen in contact. The terms "water - wet" and "oil - wet" are not only used in connection with oil sands but also in connection with other oil deposits in clastic sedimentary rocks.
Occurrence
Oil sands deposits, there are around the world, the largest are located in Venezuela and Alberta ( Canada). The oil sands reserves could account for around two -thirds of the world's oil reserves.
Orinoco oil sands
About one- third of the world's oil sand deposits are in the Orinoco heavy oil belt in Venezuela. Experts from the U.S. Geological Survey estimate the total deposits ( " in-place", ie including the technically non-degradable volume ) to 1.3 trillion barrels ( ≈ 207 km ³) of bitumen or heavy oil. The technically recoverable reserves in the Orinoco heavy oil belt is estimated at 513 billion barrels. Other sources go currently (as of May 2013) of 298 billion barrels of recoverable bitumen or heavy oil economically from. Counted among one oil sand bitumen and heavy oil deposits to the oil reserves of any country in addition, Venezuela would allow the oil- richest country in the world, ahead of Saudi Arabia.
Alberta Oil Sands
Another third with 1.8 trillion barrels of bitumen ( ≈ 286 km ³) " in-place" stored in an area of over 140,000 square kilometers in Canada's westernmost prairie province of Alberta, including the so-called Athabasca oil sands. Of these, currently (as of February 2013) are about 169 billion barrels of economically recoverable. Counted among one oil sand bitumen and heavy oil deposits to the oil reserves of any country in addition, Canada would take for a place to three of the most oil-rich countries of the world.
Other deposits
Other deposits are located in Saudi Arabia and other Middle East countries. In the U.S., the Utah oil sands are significant at 32 billion barrels. In Germany 1920-1963 oil sands of the " Wealden " ( Lower Cretaceous ) are in Wietze, in the southern Lüneburg Heath, has been degraded by mining in 220 to 250 m depth. Even with Pechelbronn in Alsace oil sand was recovered in the pit operation - there, the Eocene - Oligocene Pechelbronn lineup.
Mining and recovery
The oil sand mining can open pit or " in situ " prefix. The selection of the recovery process is based on economic considerations. The main factor is the overburden thickness.
Open-cast mining
Near-surface oil sands deposits can be extracted in open quite similar to the brown coal in Germany. In the Canadian oil sands deposits, the cost limit for the oil sands open pit at 75 m overburden thickness. In reclaimed opencast oil sand hydrocarbon fraction which must be subsequently separated from the mineral fraction.
In situ method
For deposits that are too deep below the surface, to be exploited in the mining, so-called in-situ methods are used. In situ means " in place " and refers to the fact that the hydrocarbons already underground, in the deposit separated from the mineral fraction and brought in some of these methods even in an approximately refining state.
The in- situ techniques all operate on the same principle: The long-chain are broken down into short-chain hydrocarbons. This increases the viscosity of the Kohlenwasserstoffmixtur from - it is free-flowing and can relatively easily be pumped out of the reservoir. The following list contains a variety of more or less frequently in the promotion of natural bitumen and heavy fuel oil is used in-situ method.
" Steam -assisted gravity drainage ": by the horizontal end portion of a bore is pressed steam into the deposit. This hole is referred to as the injection bore. The viscous hydrocarbons are more fluid through the heat and because they are heavier than the water vapor displaced into deeper areas of the reservoir. From there it is pumped out through a second hole, also with horizontal end portion, called the wellbore to the surface. The SAGD process is currently one of the two most commonly used in-situ techniques for the extraction of bitumen and heavy oil natural.
"Cyclic Steam Stimulation": through a single hole is pressed over days or weeks into the reservoir and then pumped through the same hole over weeks or months, the mixture of mobilized bitumen or heavy oil and steam. After the delivery cycle of new starts. The CSS method is the second of the two currently most commonly used in-situ techniques for extraction of bitumen or heavy oil.
" Toe - to - heel air injection ": This method is one of the so-called vertical- horizontal injector -producer method ( VIHP ), i.e., it makes use of a vertical injection well and a horizontal production well. In addition, it is one of the so-called in-situ combustion process (ISC ), i.e., the heat required to reduce the viscosity of the bitumen produced in the deposit by controlled combustion of a small portion of the hydrocarbons contained therein. This is pressed via the vertical injection well of air or oxygen into the formation. Either inflamed part of the flammable fraction of the bitumen or heavy oil by itself or is ignited with a burner. By continuing Act injecting air or oxygen, the fire front moves from the " toe " of the injection hole pointing towards the end of the production well to "heel ", the from the injection well end pointing away to the production well. The mobilized by the heat bitumen or heavy oil in front of the fire front is pumped through the production well. A catalyst layer on the conveyor pipe can here almost fully anticipate the so-called upgrading the bitumen, so that in fact pure crude oil can be promoted by this method from an oil sands or heavy oil reservoir ( THAI -CAPRI process, CAPRI = catalyst upgrading process in situ).
" Solvent method ": This method is not yet used for commercial production (2012 ). It closely resembles the SAGD method, however, a gaseous solvent is injected into the reservoir instead of steam which reduces the viscosity of the bitumen. The advantage over the SAGD process is that the solvent is a gas at relatively low temperatures and no energy has to be expended for the production of heat. In addition, the solvent provides for the deposition of asphaltene, particularly long chain compounds from the hydrocarbon fraction, whereby at least a part of the upgradings already taken during the conveyance anticipated also in this method.
Acts as a solvent primarily propane, as it is very cheap. Because propane However, under the pressure conditions that prevail in most deposits, liquefied, it must be mixed with another, under reservoir conditions non- condensing gas (methane, ethane, nitrogen or carbon dioxide). In addition, even steam are injected into the reservoir in order to speed up the solution process.
Preparation
Bitumen extraction
Opencast subsidized oil sands must be treated in several steps to the bitumen to separate from the mineral components. This method can be applied using hot water often. The first phase of such a hot water extraction is called " conditioning ". Here, the oil sand is first broken into smaller pieces and then mixed with hot water and sodium hydroxide. This results in a kind of tough oil sludge (English: slurry ). This is in accordance with a prior method in large rotating drums (English: tumblers ) mixed with air and sieved so that the coarsest mineral constituents are removed from the sludge. In modern plants, this step is carried out within so-called hydro - transport pipeline between the mine and the operation, in which the further extraction.
The actual separation of the bitumen from the sand takes place in so-called Primary Separation Vessels ( " Primärabscheidern "). In this gravitational separation of aerated bitumen sludge collects in a short time ( about 20 min) the top of the separator, a foamy mixture of bitumen and clay minerals (English: bitumen froth, " bitumen foam " ) and the bottom is sand and water set off (English: tailings ). In the middle, a mineral - water -bitumen mixture, known as middlings. These are fed to the secondary separation, wherein by blowing air again arise bitumen foam and tailings. In " purges " (English: de - aerators ) the bitumen foam, most of the air is withdrawn. After the bitumen is diluted with naphtha and freed by means of skew table separators and centrifuges from the water and the remaining mineral components.
" Upgrading"
The recovered by extraction or by means of in situ mining method from oil sands "clean" hydrocarbons are mostly bitumen ( asphalt) or heavy fuel oil. These are not yet available for further processing in conventional petroleum refineries suitable and must be processed by so-called upgrading to " light " crude oil (you in this case also speaks of synthetic crude oil, as this light crude oil does not come directly from a deposit ). In principle in this case the division of the long-chain hydrocarbons by temperature, catalyst, hydrogen addition ( to increase the hydrogen -to- carbon ratio ) is desired. It is then cleaned of unwanted impurities (sulfur, salt). The resulting low-sulfur " sweet crude - oil" is easy to refine and further process.
Costs and cost-effectiveness
The Canadian Athabasca oil sands mines can with the current hot water process an estimated 750,000 barrels of supply ( 119,250 m³) of crude oil per day. Because after exceeding the global oil production peak back the capacity of conventional sources of oil, unconventional oil resources such as oil sands will be used increasingly in the future for oil production. But many experts doubt that the expected production decline of conventional oil may be offset by the production of oil sands.
In 2002, the inclusion of oil sands resulted in the calculation of the economically recoverable resources to a spike in global crude oil reserves by 17.8 %, or 25 billion tonnes. However, the recovery from oil sands is not therefore to be considered equivalent to conventional petroleum and to promote the growth critical.
In 2004, 1 million barrels were ( 159,000 m³) of bitumen extracted from oil sand daily. The production costs are currently ( 2005) under $ 20 per barrel are. The cost of production of crude oil from oil sands, however, are higher and reach up to U.S. $ 40 per barrel (in 2003 ).
The cost issue is now under the company side, the biggest challenge in the exploration of Canada's Athabasca deposits. The not yet actively involved in the oil sands mining company Western Oil Sands expressed significant concern that their planned expenditure for the oil sands could get out of hand. A report of the commodity Info Service platts.com from 6 July 2006 indicate that Western Oil Sands have already passed (about 12.2 billion U.S. dollars) by 50 % its initial budget setting 13.5 billion Canadian dollars. The already fully productive companies like Suncor Energy are concerned about the costs of planned expansions.
The calculation of the costs and profitability of a production of oil sands is difficult because it is unclear to what extent environmental costs must be internalized.
Environmental impacts and climate change
Disadvantages of the method are the large water consumption, the energy required to generate the steam, the problem of cleansing, possible underground environmental damage and the loss of forests and peatlands. Critics argue that the massive water consumption of a production is on a large scale in the way. Proponents argue that technical improvements will increase the efficiency of water use.
The mining extraction of oil sand has a direct impact on the local and global ecosystems. In Alberta, this form of oil extraction completely destroys the boreal forest, bogs, rivers and the natural landscape. It is doubtful that will ever develop the existing natural ecosystem back in the mining areas. Despite the mining industry, which have the recovery of the boreal forest in Alberta to target projects, none of the areas has been certified as " recovered " more than 30 years after the onset of degradation.
For each barrel of synthetic oil produced more than 80 kilograms of greenhouse gases released into the atmosphere and about 4 barrels of waste water are discharged into ponds. The expected growth of crude oil production in Canada threatens its international obligations. When Canada the Kyoto Protocol confirmed, it was agreed to reduce its greenhouse gas emissions by 6 percent decrease by 2012. Nevertheless, had increased greenhouse gas emissions in Canada around 2002 by 24 percent. As The Guardian reported on 27 October 2011, Canada will be supported in its mining plans over the expected EU environmental requirements by the British government secretly.