Oil sands

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Oil sands from Southern California (Monterey Formation, Miocene)

Oil sand or tar sand is a mixture of various mineral grains, mostly the size of sand grains, mostly consisting of quartz , a petroleum with a depleted amount of volatile components and water . Depending on the viscosity and degree of depletion, this oil is referred to as natural heavy oil (still relatively liquid) or natural bitumen (very tough or solid). What oil sands have in common is their storage at a relatively shallow depth (a few 100 m). Often are they even directly at the surface. Sandstones that are stored at a greater depth and from which refinable , “light” crude oil can be extracted without special extraction processes are more likely to be regarded as oil- rich or oil- bearing sandstones than oil sands .

The world's most important oil sands deposits are in Canada and Venezuela . Oil sands located on or very close to the earth's surface are mined in open-cast mining. Bitumen or even relatively “light” crude oil can be extracted from deeper-lying oil sands using so-called in-situ methods (e.g. the injection of water vapor into the reservoir). In Lower Saxony and the Upper Rhine , oil sands were also mined underground .

In the course of rising oil prices and technical progress, the extraction of synthetic crude oil from oil sands is becoming more and more profitable. The government of Canada promotes the exploitation of oil sands and sees this as an important economic factor that will secure the future. In 2011, oil sands provided a good 10% of the world's crude oil.

Origin and composition

General

It is assumed that oil sands arise in most cases when a sandy, more or less consolidated sedimentary rock is impregnated with a small proportion of primary organic carbon from crude oil rising from the depths. This is an important difference to oil shale , which is a rather fine-grain ( pelitic ) potential petroleum mother rock with a high proportion of primary organic carbon. Most oil sand deposits are therefore nothing more than near-surface oil deposits. When the crude oil came into contact with oxygen and the volatile, short-chain components were lost, the oil, which was originally relatively low-viscosity, was naturally converted into tough bitumen. The oil has either migrated directly from the host rock to near-surface sediments or comes from a primary deposit below the oil sands deposit. Oil sands are therefore often found in areas where there are also “real” (conventional) oil deposits.

However, some oil sands could also have arisen directly from organic-rich, sandy sediments and thus belong to an independent form of hydrocarbon deposits .

The mineral fraction consists mainly of quartz, to a lesser extent also of other minerals, e.g. B. feldspar , mica , rutile , zirconium , tourmaline or hematite and clay minerals, such as. B. kaolinite . The proportion of hydrocarbons in the sands is between one and 18%. Degrading oil sand with a hydrocarbon content of less than 6% is technically possible, but currently (as of 2007) uneconomical. On average, one barrel (159 liters) of crude oil is extracted from 2 tons of oil sand .

"Hydrophilicity" of oil sands

Schematic representation of "hydrophilic" oil sands

Some oil sands are referred to as " hydrophilic " (also water-wet , ' water- wetted') in terms of their composition . The characterization as “hydrophilic” is misleading, however, since hydrophilicity is a property of surfaces or, on a smaller scale, of molecules. However, oil sand is a mixture of the most varied of substances, the surfaces or molecules of which are partly hydrophilic but partly hydrophobic. Oil sands should therefore not be identified by the term “hydrophilic”. The more apt attribute in this case is “ water-wet ”.

" Water-wet " means that the mineral grains are not in direct contact with bitumen, but should be covered by a more or less closed, thin film of water. However, so far there is no direct evidence that such water films actually exist between bitumen and mineral grains. The hypothesis of the existence of such water films is supported by the fact that many clean mineral surfaces, u. a. those of quartz, are actually hydrophilic. If the sediment body was saturated with water before impregnation with oil, water would remain on the grain surfaces due to the hydrophilicity of the quartz grains. Even water that subsequently penetrated the oil sand would accumulate on the quartz grains due to the hydrophilicity of the quartz grains. The applicability of hot water extraction is also evidence that an oil sand is “ water-wet ”.

The opposite of “ water-wet ” is “ oil-wet ”. " Oil-wet " means that the grain surfaces are "dry" or are in direct contact with the bitumen. 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

Extension of the Orinoco heavy oil belt (blue line) and the Eastern Venezuelan petroleum province (red line).
Oil sands deposits in Alberta, Canada

Oil sands deposits are around the world, the largest are located in Venezuela and Alberta ( Canada ). The oil sands reserves could make up around two thirds of the world's oil reserves.

Orinoco oil sands

Around a third of the world's oil sands are located in the Orinoco heavy oil belt in Venezuela. Experts of the US Geological Survey estimate the total deposits (" in-place ", ie including the technically non-degradable volume) at 1.3 trillion barrels (≈ 207 km³) bitumen or heavy oil. The technically recoverable reserves in the Orinoco heavy oil belt are estimated at 513 billion barrels. Other sources currently (as of May 2013) assume 298 billion barrels of economically recoverable bitumen or heavy oil. If one added oil sand bitumen and heavy oil deposits to a country's oil reserves, Venezuela would be the most oil-rich country on earth, ahead of Saudi Arabia.

Alberta oil sands

Another third with 1.8 trillion barrels of bitumen (≈ 286 km³) is stored in an area of ​​140,000 km² under the boreal coniferous forests in northern Canada's westernmost prairie province of Alberta. These include the so-called Athabasca oil sands . Of this, around 169 billion barrels were considered economically viable in February 2013. Including the oil sand / bitumen and heavy oil deposits, Canada is the country with the third largest oil deposits on earth.

More deposits

There are other deposits in Saudi Arabia and other Middle Eastern countries . In the USA , the Utah oil sands are significant with 32 billion barrels. In Germany in Wietze , south of the Lüneburg Heath , 1920-1963 oil sands of "Wealden" (Lower Cretaceous) by mining in 220 to 250 m depth mined Service. At Pechelbronn in Alsace , oil sands were also extracted in the mine - there from the Eocene-Oligocene Pechelbronn Formation .

Mining and extraction

Part of the open pit mine as well as sulfur dumps and waste water basins of the processing plant "Mildred Lake" of Syncrude Canada Ltd. in the Athabasca oil sands district, Alberta, Canada.

The oil sands can be extracted in an open pit or " in situ ". The selection of the extraction process is based on economic aspects. The main factor is the thickness of the overburden.

Open pit

Oil sand deposits close to the surface can be extracted in open-cast mining, much like lignite in Germany. In the Canadian oil sands deposits, the profitability limit for oil sands extraction in open-cast mining is 75 m thick overburden. In the case of oil sands extracted from open-cast mining, the hydrocarbon fraction must be subsequently separated from the mineral fraction.

In-situ procedure

SAGD Producing Well.jpg
Saleski Pilot Steam Generator.jpg
Delivery probe (above) and steam generator (below) of a SAGD plant in the Athabasca oil sands district in Alberta

So-called in-situ methods are used for deposits that are too deep below the surface to be exploited in open-cast mining . In situ means “on the spot” and refers to the fact that the hydrocarbons are already separated from the mineral fraction underground in the deposit and, in some of these processes, are even brought into a state that is almost ready for refining.

The in-situ techniques all work on the same principle: The long-chain ones are broken down into shorter-chain hydrocarbons. This reduces the viscosity of the hydrocarbon mixture - it becomes more flowable and can be pumped out of the deposit relatively easily. The following list contains a selection of in-situ processes that are more or less frequently used in the extraction of bitumen and natural heavy oil.

SAGD ( steam assisted gravity drainage )

"Steam-assisted gravity drainage": Water vapor is pressed into the deposit through the horizontal end section of a borehole. The technical process of pressing in is also called injection and the corresponding hole is therefore referred to as an injection hole. The viscous hydrocarbons become thinner due to the heat and, as they are heavier than the water vapor, displaced into deeper areas of the reservoir. From there, they are pumped to the surface via a second bore with a horizontal end section, the so-called delivery bore. The part of the pore space above the injection hole that is increasingly filling with steam is called the steam chamber . The SAGD process is currently one of the two most widely used in-situ techniques for extracting bitumen and natural heavy oil.

CSS ( cyclic steam stimulation , "huff 'n' puff")

"Cyclical steam stimulation": Steam is pressed into the deposit through a single borehole for days or weeks and then the mixture of mobilized bitumen or heavy oil and water is pumped out through the same borehole for weeks or months. The funding cycle is then started again. The CSS process is the second of the two most frequently used in-situ techniques for the extraction of bitumen and heavy oil.

THAI ( toe to heel air injection )

"Toe-to-heel air injection": This process is part of the so-called Vertical Injector Horizontal Producer (VIHP) process . that is, it uses a vertical injection well and a horizontal production well. It is also one of the so-called in-situ combustion processes (ISC), i.e. That is, the heat necessary to reduce the viscosity of the bitumen is generated in the reservoir by the controlled combustion of a small part of the hydrocarbons contained therein. Here, air or oxygen is pressed into the deposit via the vertical injection borehole. Either part of the easily flammable fraction of the bitumen or heavy oil ignites by itself or is ignited with a burner. As air or oxygen continues to be injected, the fire front moves from the “toe”, the end of the production well pointing towards the injection well, to the “heel”, the end of the production well pointing away from the injection well. The bitumen or heavy oil mobilized by the heat in front of the fire front is pumped out via the production well. A catalyst layer on the conveying pipe can almost completely anticipate the so-called upgrading of the bitumen, so that virtually pure crude oil can be conveyed from an oil sand or heavy oil deposit using this process ( THAI-CAPRI process , CAPRI = catalyst upgrading process in situ ).

VAPEX ( vapor extraction process )

“Solvent process”: This process has not yet (2012) been used for commercial production. It is very similar to the SAGD process, but instead of water vapor, a gaseous solvent is injected into the deposit, which reduces the viscosity of the bitumen. The advantage over the SAGD process is that the solvent is gaseous at relatively low temperatures and hardly any energy has to be used to generate heat. In addition, the solvent ensures the separation of asphaltenes , particularly “heavy” complex compounds, from the hydrocarbon fraction, which means that at least part of the upgrading is already anticipated during the production of this process .

The main solvent used is propane because it is very cheap. However, because propane liquefies under the pressure conditions that prevail in most storage facilities, it must be mixed with another gas that does not condense under storage conditions (methane, ethane, nitrogen or carbon dioxide). In addition, water vapor can also be injected into the deposit in order to accelerate the dissolution process.

processing

Bitumen extraction

Mildred Lake Oil Sands Processing Plant in the Athabasca Oil Sands District, Alberta, Canada. The associated opencast mine can be seen in the background.

Oil sands extracted from opencast mines must be treated in several steps in order to separate the bitumen from the mineral components. Methods using hot water are often used here. The first phase of such a hot water extraction is called “ Conditioning ”. The oil sand is first broken into smaller pieces and then mixed with hot water and sodium hydroxide . This results in a kind of viscous oil sludge ( slurry ). According to an older process, air is added to this in large rotating drums (English: tumblers ) and sieved, which removes the coarsest mineral components from the sludge. In more modern plants, this work step takes place within so-called hydrotransport pipelines between the opencast mine and the plant in which the further extraction takes place.

The actual separation of the bitumen from the sand takes place in so-called primary separation vessels (“primary separators”). With this gravitational separation of the bitumen sludge mixed with air, a foamy mixture of bitumen and clay minerals collects in a short time (approx. 20 min) in the separator and sand and water settle at the bottom (English: tailings ). A mixture of mineral, water and bitumen, the so-called middlings, remains in the middle . These are fed to the secondary separation, which in turn creates bitumen foam and tailings by blowing in air . Most of the air is withdrawn from the bitumen foam in " de-aerators" . Then the bitumen is diluted with naphtha and freed from water and the remaining mineral components using inclined table separators and centrifuges .

"Upgrading"

The “clean” hydrocarbons obtained from oil sands by extraction or by means of in situ degradation processes are mostly bitumen (asphalt) or heavy oil. These are not yet suitable for further processing in conventional oil refineries and have to be processed through so-called upgrading . In the best-case scenario, the “light” and low-viscosity product of the upgrade is also known as synthetic crude oil ( SCO), as it does not come directly from a conventional crude oil reservoir , unlike the actual crude oil . In principle, the aim here is to split the long-chain hydrocarbons through temperature, catalysts, addition of hydrogen or carbon deposition (to increase the hydrogen-to-carbon ratio). Then it is cleaned of unwanted accompanying substances (sulfur, salt). The resulting low-sulfur "sweet crude oil" is easy to refine and further process.

So that the upgrading does not necessarily have to be carried out at the mining site and the cleaned raw bitumen can also be conveniently delivered directly via pipeline to an appropriately equipped refinery complex, its viscosity must be reduced. This is usually achieved by adding either “light” synthetic crude oil or a volatile hydrocarbon mixture - for example naphtha  . The resulting relatively handle low Rohbitumengemische be Synbit (of English. Syn thetic crude + bit umen ) or Dilbit (of English. Dil uted bit umen called).

Cost and economy

Canada's Athabasca oil sands mines can produce an estimated 750,000 barrels (119,250 m³) of crude oil per day using the current hot water process. Since the capacity of conventional oil wells declines after the global maximum oil production has been exceeded , unconventional oil resources such as oil sands will increasingly be used for oil production in the future. However, many experts doubt that the production of oil sands can compensate for the expected decline in production of conventional oil.

In 2002, the inclusion of oil sands in the calculation of economically recoverable resources led to a surge in global oil reserves of 17.8% or 25 billion tons. However, the extraction from oil sands is not equivalent to the extraction of conventional crude oil, because compared to other crude oil extraction methods, the extraction of oil sands has a significantly lower harvest factor . While only about 1–2% of the energy contained in the oil was used for the extraction of the first oil wells, about a third to a quarter of the energy contained in them has to be used for oil sands. The harvest factor is therefore only 3 to 4. The inclusion of oil sand deposits in the estimate of the oil reserves must therefore be viewed critically.

In 2004, 1 million barrels (159,000 m³) of bitumen were extracted from oil sands every day. The production costs are currently (as of 2005) under 20  US dollars per barrel. The production costs of crude oil from oil sands, however, are higher and amount to up to 40 US dollars per barrel (as of 2003).

The question of costs has now become the company's greatest challenge in exploring the Canadian Athabasca deposits. Western Oil Sands , which is not yet actively involved in oil sands extraction, expressed concern that its planned expenses for oil sands extraction could get out of hand. According to a report by the Platts commodity information service on July 6, 2006, Western Oil Sands has already exceeded its initial budget of 13.5 billion Canadian dollars (approximately 12.2 billion US dollars) by 50%. Even the already fully productive companies like Suncor Energy are concerned about the cost of planned expansions.

It is difficult to calculate the costs and economic viability of extracting oil sands, as it is unclear to what extent ecological costs have to be included. The future of oil sands exploitation in Alberta is also uncertain, as the rapid spread of the fracking process - especially in the USA - makes the profitability of mining increasingly unlikely.

Effects on the environment and climate

General

The mining of oil sands in opencast mining, bitumen extraction and the processing of bitumen into synthetic crude oil that can be refined, but also the in-situ extraction of oil from oil sands generally have a significantly poorer ecological balance than conventional crude oil production. Detrimental effects on the environment and the climate result primarily from the high water consumption and, in particular, from the large quantities of wastewater and the high energy demand. Every barrel of synthetic oil produced produces more than 80 kilograms of greenhouse gases and around four barrels of wastewater. In the case of mining in open-cast mining, there are also drastic effects on local ecosystems . The breakdown of oil sands is also associated with a strong release of secondary organic aerosols . These are an important component of fine dust and, as air pollutants, have an impact on air quality , but also have an impact on the climate. Canadian oil sands mining is responsible for production of 45 to 84 tons per day, making the open pit mines one of the largest sources of secondary organic aerosols in North America .

Situation in Alberta

In Alberta, open pit mining of oil sands completely destroys boreal forest , bogs , rivers and other elements of the natural landscape in the mining area. However, oil sands extraction in open-cast mining in Alberta is only possible on an area of ​​4800 km² (3.3% of the total area with oil sand deposits underground) of which only 767 km² were actually occupied by open-cast mines as of December 31, 2012 (0.2% of the Total area of ​​Alberta's boreal forest). Furthermore, the mining companies in Alberta are obliged to return the areas used to a natural state after the pits and processing plants have been closed . However, it can take more than 15 years before a functioning ecosystem is restored in the affected areas. In addition, pollutants from the opencast mines and the oil sands processing plants can get into the environment during operation. The in-situ extraction of the oil sands generally has a significantly lower impact on the local environment.

Representation of the distribution of the CO 2 concentration in the air above normal during a measurement flight over an open-cast mine complex in the Athabasca oil sands in 2013

The increase in oil production from oil sands and the associated increase in greenhouse gas emissions ultimately led Canada to withdraw from the Kyoto Protocol , in which it committed to reducing its emissions by 6 percent by 2012 compared to 1990 levels. However, by 2010, Canada's greenhouse gas emissions had increased 17.4% since 1990. In addition, measurements made in the air above the oil sands opencast mines in Alberta in 2013 suggest that the CO 2 emissions generated by oil sands mining are in some cases far higher than the previously customary and internationally recommended ground-level measurements suggest .

literature

  • GV Chilingarian, TF Yen (Eds.): Bitumens, Asphalts and Tar Sands. Developments in Petroleum Science. Vol. 7, Elsevier, Amsterdam (et al.) 1978, ISBN 978-0-444-41619-3
  • AG Oblad, JW Bunger, FV Hanson, JD Miller, HR Ritzma, JD Seader: Tar Sand Research and Development at the University of Utah. Annual Review of Energy. Vol. 12, 1987, pp. 283-356, doi : 10.1146 / annurev.eg.12.110187.001435
  • Oil Sands Discovery Center (Ed.): Facts about Alberta's oil sands and its industry. Fort McMurray, Canada 2016 ( PDF 2 MB)
  • Ludger Bastien, H. Peter Dörrenbächer, Petra Dolata: The natural potential of Canada. In: Ursula Lehmkuhl (Ed.): Country Report Canada. Federal Agency for Civic Education (BpB), Bonn 2018, p. 275 f. (Info box oil / tar sands in Alberta and pipeline construction in British Columbia ).

Individual evidence

  1. ^ A b John Liggio, Shao-Meng Li, Katherine Hayden and 22 other authors: Oil sands operations as a large source of secondary organic aerosols. Nature. Vol. 534, 2016, pp. 91-94, doi: 10.1038 / nature17646
  2. ↑ a b c Jan Czarnecki, Boryan Radoev, Laurier L. Schramm, Radomir Slavchev: On the nature of Athabasca Oil Sands. Advances in Colloid and Interface Science. Vol. 114-115, 2005, pp. 53-60, doi : 10.1016 / j.cis.2004.09.009
  3. ↑ CJ Schenk, TA Cook, RR Charpentier, RM Pollastro, TR Klett, ME Tennyson, MA Kirschbaum, ME Brownfield, JK Pitman: An estimate of recoverable heavy oil resources of the Orinoco Oil Belt, Venezuela. US Geological Survey Fact Sheet 2009–3028, US Department of the Interior / US Geological Survey, 2009, 4 pp. ( Online )
  4. ^ A b Oil Sands - A Strategic Resource for Canada, North America and the Global Market. Energy Security and Economic Benefits. Natural Resources Canada, 2013, ( PDF 2.8 MB)
  5. ↑ Note: Since heavy oil and bitumen deposits are becoming more and more important to the oil industry. a. Because the increasing shortage of conventional crude oil and technical progress make the extraction of crude oil from natural heavy oil and bitumen more and more economical, such deposits are actually increasingly included in the official statistics in the respective national oil reserves.
  6. ^ Alberta (Canada) - Oil Sands Extraction . United States of America (USA), Canada - Economy. In: Diercke World Atlas, Maps & Information for Geography . Westermann, Braunschweig 2015, ISBN 978-3-14-100800-5 , p. 214 ( diercke.de [accessed on April 25, 2017] Fig. 1, scale 1: 6,000,000).
  7. ^ Oil Sands - A Strategic Resource for Canada, North America and the Global Market. (PDF 3.1 MB) Natural Resources Canada, 2013, accessed April 25, 2017 .
  8. ↑ Thomas Joerdens: Oil production in Wietze 50 years ago - museum recalls industrial history. Weser-Kurier from October 13, 2013
  9. ↑ Titus Kockel: Geology and German Oil Policy, 1928 to 1938 - the early career of the petroleum geologist Alfred Theodor Bentz. Dissertation to obtain the academic degree of Doctor of Philosophy (Dr. phil.). Faculty I (humanities) at the Technical University of Berlin. Berlin, 2003, p. 44 f., Urn : nbn: de: kobv: 83-opus-6747
  10. ↑ H. Monke: Economic Development and geology of the German oil deposits. S. 193–205 in: K. Flegel (Ed.): The development of the German coal and steel industry from 1860–1912. Royal Prussian Geological State Institute, Berlin 1915 ( PDF 1.9 MB)
  11. ^ Qing Chen: Assessing and Improving Steam-Assisted Gravity Drainage: Reservoir Heterogeneities, Hydraulic Fractures, and Mobility Control Foams. PhD dissertation, Stanford University, Department of Energy Resources Engineering, Stanford (CA) 2009 ( PDF 6.8 MB), p. 11 ff.
  12. ↑ Abarasi Hart: The novel THAI-CAPRI technology and its comparison to other thermal methods for heavy oil recovery and upgrading. Journal of Petroleum Exploration and Production Technology. 2013 (article in print, currently only available online), doi : 10.1007 / s13202-013-0096-4 ( Open Access )
  13. ↑ a b Farshid Torabi, Benyamin Yadali Jamaloei, Blair M. Stengler, Drew E. Jackson: The evaluation of CO 2 -based vapor extraction (VAPEX) process for heavy oil recovery. Journal of Petroleum Exploration and Production Technology. Vol. 2, No. 2, 2012, pp. 93-105, doi : 10.1007 / s13202-012-0025-y ( Open Access )
  14. ↑ Michael Toman, Aimee E. Curtright, David S. Ortiz, Joel Darmstadter, Brian Shannon: Unconventional Fossil-Based Fuels: Economic and Environmental Trade-Offs. RAND Corporation, 2008, p. 15 f. (Chapter Oil Sands and Synthetic Crude Oil ; JSTOR )
  15. ↑ See Ferdi Schüth: Fundamentals of the Energy Discussion. P. 15–31 in: Peter Gruss, Ferdi Schüth (Ed.): The future of energy. The answer of science. A report from the Max Planck Society. Munich 2008, p. 25.
  16. ↑ Craig Morris: Esso proclaims the "Oil Dorado 2003" , Telepolis, June 20, 2003
  17. ^ Dionys Zinc: landslide in Alberta . In: Coyote , No. 27th year - 106, Action Group Indians & Human Rights eV, Munich Summer 2015, ISSN  0939-4362 , pp. 25–26.
  18. ^ Peter Mettler: Petropolis. Aerial Perspectives on the Alberta Tar Sands. Documentary, Canada 2009
  19. ^ A b Alberta’s Clean Energy Future: Reclamation. Government of Alberta, archived from the original on September 25, 2014 ; accessed on October 7, 2014 (English).
  20. ↑ Joshua Kurek, Jane L. Kirk, Derek CG Muir, Xiaowa Wang, Marlene S. Evans, John P. Smol: Legacy of a half century of Athabasca oil sands development recorded by lake ecosystems. Proceedings of the National Academy of Sciences of the United States of America. Vol. 110, No. 5, 2013, pp. 1761–1766, doi : 10.1073 / pnas.1217675110
  21. ↑ Canada pulls out of Kyoto protocol. The Guardian, Nov. 13, 2011
  22. ↑ United Nations Framework Convention on Climate Change (UNFCCC): Report of the individual review of the annual submission of Canada submitted in 2012 (FCCC / ARR / 2012 / CAN). UNFCCC, Bonn 2013, p. 3 u. 5 ( PDF 550 kB)
  23. ↑ John Liggio, Shao-Meng Li, Ralf M. Staebler, Katherine Hayden, Andrea Darlington, Richard L. Mittermeier, Jason O'Brien, Robert McLaren, Mengistu Wolde, Doug Worthy, Felix Vogel: Measured Canadian oil sands CO 2 emissions are higher than estimates made using internationally recommended methods. Nature Communications. Vol. 10, 2019, Article No. 1863, doi: 10.1038 / s41467-019-09714-9 ; see also: Oil sands in Canada release more CO 2 than is known. Der Standard, April 24, 2019

Web links

Wiktionary: Oil sands  - explanations of meanings, word origins, synonyms, translations
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