Bituminous sand

Description

These formations at a shallow depth (sometimes almost with the outcrop) contain of 80 with 85 % of mineral matters (Silica and Clay), of 10 with 12 % of natural Bitumen and 5 % of Water. This bitumen is not strictly speaking oil, because it is at least hundred times more viscous and definitely denser.

Conventional oil consists of light compounds, such as gas, the gasoline, the kerosene and the gases oily. Also, it consists of heavy compounds, such as the lubricating oils, heavy fuels and the bitumen. These compounds have from 3 to 300 atoms of carbons and the points of boilings going of -10 with 525°C.

The origin of the bitumen is dubious. It is too much viscous to have migrated in its actual position. One thus thinks that it acted, at the origin, of conventional oil which, after having migrated in tanks too not very deep to isolate it from the outside world, was degraded, losing thus his lightest compounds by evaporation, aggression Bactérie and “ lavage ” with water. This explanation does not achieve however the unanimity.

The bitumen resembles somewhat the residual fuel resulting from the distillation of the conventional crude: it almost does not contain a Alcane S courts but much of complex, polycyclic hydrocarbons for example.

Distributions

The reserves are strongly concentrated in two geological provinces.

It is in the north of Alberta that the principal bituminous sand layers are. In the west, in Peace To rivet, in the south, Cold Lake and in north, close to the river of Athabasca, more precisely at the height McMurray. Nearly 20 companies are located in Alberta, including two more important: Syncrude and Suncor. Moreover, to compare with equality this bitumen with conventional crude oil reserves, it is necessary to deduce energy necessary to its extraction and its transformation.

In Venezuela, the " ceinture" of Orénoque, probably the greatest contiguous accumulation of hydrocarbons in the world, contains about same volume. As dense but more liquid as the bitumen of the Canadian layers, it is often classified like extra-heavy crude and not like bituminous sands.

The reserves existing elsewhere in the world are much smaller. There exists a vast layer in Siberia Orientale, in the area of Olenek, but practically no information is available about it. It is located on the Arctic coast, the extreme climate and insulation explain why its exploitation is not considered for the moment.

Reserves of small size exist in at least about fifty country.

Techniques of exploitation

It is into 1778 that Peter Pond located the first sources of Bitume in the area of Athabasca, but it is Robert Fitzsimmons, a contractor, who is the first to have separated the bitumen from the sand and which used it to cover the roads and the roofs. If the Amerindian S have since centuries used this bitumen to block up boats, bituminous sands really drew the attention of oil industry only after the oil crises.

Three stages are important to obtain the bitumen. The first stage consists with the exploitation of bituminous sands. This stage can be done either by mining extraction, or by in situ extraction. The second stage consists with the extraction of the bitumen of bituminous sands, which is done especially by the process with warm water. Since the bitumen is not conventional oil, it thus should be transformed. The third stage is thus the transformation of the bitumen, which is made various ways.

Mining extraction

The crude oil reserves of Athabasca represent more than 300 billion barrels. Sand contains on average bitumen 11,5%. It is thus necessary to exploit a gigantic quantity of bituminous sands, in order to obtain a high quantity of bitumen. Indeed, the recovery of two tons bituminous sands makes it possible to obtain only one bitumen barrel. The exploitation of bituminous sands is thus done by digging holes in the ground and this, 24 hours over 24,7 days out of 7, winter like summer. A major problem is observed at the time of the mining of bituminous sands. Since bituminous sands are located in great depth under the ground, it is first of all necessary to shave all the northern forest to remove the compost of surface and to put it side. Thereafter, one digs to it dead ground, which is with approximately a 50 meters depth. Ground death is removed, until attack of bituminous sands which one extracts. All this process is carried out using trucks of 365 tons and the colossal cranes, whose shovelfuls make 100 tons.

As for the exploitation of the other mineral resources with open sky, the operator must give in state the grounds after the exploitation.

Sand is transported thereafter to the various factories of extraction of the bitumen. The extraction of the bitumen is done by the process with warm water, developped at the point by Karl Clark in 1929. This process consists in placing bituminous sand in enormous rotary drums and mixing it with warm water and vapor. The bitumen separates from sand and binds to the bubbles of air. The whole is filtered and deposited in conical containers of forms allowing separation. The bitumen related to the air is collected in the form of foam, containing oil 65%, water 25% and 10% of solids. After having mixed the whole using large centrifugal machines, three layers are observed. The large sand particles settle at the bottom, which are pumped towards a discharge and are used in the construction of the dams. The transition course consists of a mixture of water, small bitumen particles and some minerals, which one calls mixed. This intermediate water is withdrawn and pumped in order to re-use them in the process of extraction. Lastly, the bitumen floats on the surface, which makes it possible to recover it with a percentage from 88 to 95%.

In situ extraction

In situ new technology is used to counter the various environmental problems. In situ extraction allows the separation of the bitumen and sand in the same tank. The latter consists of horizontal wells, which are dug in the ground and which make it possible to inject steam to low pressure. Following this injection, the temperature of the bitumen increases, involving a reduction in its viscosity. Thus, the bitumen softens and is easily pumped. In situ extraction can be done according to two different processes, that is to say by Cyclic Steam Simulation (CSS) or Steam Assisted Gravity Drainage (SAGD).

The first solution was the process CS (Cyclic Steam Simulation). It consists in alternatively using the same well in vapor injection and bitumen extraction. The vapor liquefies the bitumen and makes pumping possible. Compared to the mining extraction, one disturbs only one very small surface on the ground, and the general harmful effects (noise for example) are quite less. However the consumption of energy to produce the vapor is enormous.

The technique SAGD ( Steam Assisted Gravity Drainage ), which did not reach its phase of maturity yet, uses horizontal wells associated two to two. The well of the top injects vapor permanently while that of the lower part collects water and bituminizes. Contrary to the process CS, the quantity of vapor to be injected for a production of bitumen given is less, which improves the energy assessment, but this solution cannot apply everywhere: one needs a good vertical homogeneity of the tank so that the flow is established.

In situ extraction is done more and more since the year 2000. The bitumen recovered in situ in 2000 represented 40.000 m3, while in 2006, the bitumen recovered by this technique reached 75.000 m3. Today, a little more than 12% of the bitumen is recovered by in situ extraction and years by years, this proportion will increase. The disadvantages connected to this method of extraction rest on the fact that it is very expensive and that no environmental impact is known for the moment.

Commercial transformation

That it comes from mining extraction or in situ , the bitumen is not directly marketable on the oil market, in particular because it is too viscous to be transported by drain. Two methods are possible to make the bitumen saleable. Simplest is to mix it with approximately light hydrocarbon 30% (condensates of natural gas or naphtha), which to some extent comes to replace short hydrocarbons that it misses with this form oil. This practice butts nevertheless against the cost of the thinner, and Canada would be quickly in shortage of condensates if he wanted to use million barrels per day of bitumen in this way.

The second method, which is more complex, consists in converting the bitumen into syncrude, a marketed oil mark. Compared to conventional crude oil, the bitumen is composed of far too much carbon, but not enough hydrogen. The bitumen thus should be transformed chemically, to obtain a mixture of hydrocarbons close to an crude oil of good quality. The techniques are connected with those employed to improve the residual fuels of the refineries. This thus implies three stages. First of all, coking consists in extracting carbon by thermal process. Using large furnaces, called coqueurs, the bitumen is heated with 468-498°C, which involve the cracking of the heavy fractions, thus producing lighter fractions such as the gasoline, the fuel gases and the petroleum coke. This stage can also be done using a solvent (de-asphalting) or other chemicals. De-asphalting rests on the principle of the destabilization of the bitumen in the presence of solvents, such as light propane or other hydrocarbons. The heavy compounds and the light compounds separate according to their difference in solubility opposite solvent used, without their chemical structure being degraded. The second phase of the transformation, the hydrocraquage, consists in adding hydrogen, in order to obtain distillates of better quality. The hydrocraquage makes it possible to increase the production of the liquids and to reduce the levels of sulfur dioxide emission. The principal disadvantage of the hydrocraquage rests on the fact that hydrogen must necessarily come from natural gas, which will increase the gas emissions with greenhouse effect. Moreover, this stage requires much energy.

Lastly, the last stage, which is the hydro-treating, rests on the withdrawal of oxygen and nitrogen, sulfur molecules, allowing the improvement of the molecular characteristics of hydrocarbons. The result is a syncrude light and low in sulfur, which, contrary to a mixture naphtha-bituminizes, can be used by any refinery. The hydro-treating requires installations of factories which are very expensive, allowing the manufacture of hydrogen, the sulfur dioxide washing and the recovery of sulfur.

Environmental impact

The mining extraction of bituminous sands has an significant impact on the ecosystem S. In Alberta, this form of extraction destroys completely, as of the opening of the mine with open sky, the northern forest, and has direct consequences on the air. Hundreds of km2 of territories are devastated. The life of the northern forest comes from the ground, which is composed of essential biological ingredients. By shaving the northern forest and by destroying the ground, there is destruction of these biological ingredients essential with the life of the northern forest. Mining industry considers that the northern forest will take again its place on the grounds restored after the period of extraction, but no ground is considered “ restauré ” some thirty years after the opening of the first mine in the area of Strong McMurray in Alberta.

Moreover, the extraction of bituminous sands releases from the polluting agents, such as methane. Also, the northern forest is made up of peat bogs, which are natural carbon dioxide basins. By destroying the forest, one destroys these peat bogs, which generates an increase in the gas emissions with greenhouse effect.

Moreover, the extraction of only one barrel of petrol of bituminous sands of Alberta generates more than 80 kg of Gaz to greenhouse effect (GES). The exploitation of bituminous sands generates very harmful gases, such as the sulfur dioxide, which is responsible, even with very small quantities, acidification of the lakes and forests. In 2003, Alberta was named the capital of the atmospheric pollution of Canada with a generation of more than one billion kilograms of gas emissions to greenhouse effect. By producing a barrel of petrol extracted bituminous sands, one generates three times more gas emissions with greenhouse effect than the production of a traditional barrel of petrol. Today, the company of exploitation of bituminous sands Suncor rejects 600 tons of natural gas per hour.

Growth envisaged of the production of synthetic oil albertain threat also international engagements of Canada. By ratifying the Protocol of Kyoto, Canada committed itself reducing, from here 2012, its emissions of GES of 6 pourcent compared to the year under review (1990). Instead of the reduction in the GES, an increase of 145 megatons of the emissions of GES will be observed, of which the quarter would come from the exploitation of bituminous sands. In 2002, its emissions were higher of 24 pourcent at the year under review.

The extraction of the bitumen of bituminous sands has direct consequences on water and the air. A great quantity of water is necessary for the process with warm water, that is to say from 2 to 5 fresh water barrels to produce only one barrel of petrol. It is thus necessary to draw this water in the great rivers, which will involve a draining of the grounds and a fall of the ground water. The waste water, which is a very toxic mixture, is rejected into the basins located close to the Athabaska river. Fishing, being the source of subsistence of the community, is thus impossible to practice, since the water of the river is polluted too much. Also, this water with fatal consequences for the animals. It is thus necessary to prevent the animals from approaching the river. Also, the waste water can be used for the rehabilitation of the territory, which was disturbed. However, this water is very polluted, since it contains more than 250 toxic different ingredients, such as methane, xylene, benzene, mercury, arsenic and other hydrocarbons. With time, there is a bio-accumulation of these chemicals, but the concentration is not known. Toxicity thus develops, since the majority of the chemicals do not disappear and do not degrade themselves biologically.

Once again, the heating of bituminous sands, in goal to extract the bitumen, requires much natural gas, which will increase the gas emissions with greenhouse effect. 10 years ago, 16 million tons of gas with greenhouse effect were rejected during the heating of bituminous sands and in 10 years, they will be 65 million tons of gases with greenhouse effect, which will come from the same source. Moreover, one unpleasant odor makes people sick and this air pollution is involved towards the provinces of the East of the country, thus causing acid rains.

Several solutions are being studied and in progress to counter these environmental disadvantages. The companies of exploitation of bituminous sands have three objectives to reach, that is to say the improvement of the recovery of water, the reduction of the use of heat and water and finally, the reduction and the elimination of the residue basins. Several solutions are being studied, such as the extraction of the bitumen by the heating, by the injection of solvents or chemicals, by boulettage and sieve oléophiles. However, the long-term advantages and disadvantages are not yet known. It is thus impossible to use these methods. Chimneys are developed at present, to make it possible to reduce the sulfide dioxide emissions from approximately 90%. On the other hand, the increase in the production of oil will eliminate this reduction from the sulfur dioxide emissions. In situ extraction is also used.

In spite of the consequences of the exploitation of bituminous sands, the increase in the production of the bitumen has several advantages. Even if the Canadian government invests more than 25 billion dollars from here 2020 for the exploitation sands, a profit of more than 100 billion dollars will be injected in the Canadian budget and more than 44.000 established posts will be created in all the country. It should not be forgotten that oil is a very profitable product. The production of a barrel of petrol can cost between 10$ and 13$ and are sold to 30$.

Analytical aspect

The grounds are affected after the process of extraction of the bitumens of sands by the waste water which is rejected after being used. This water, for the majority, is cleaned but those which cannot the being are kept in tanks to be re-used in the process of extraction or they are used for the rehabilitation of the territory. This last is the principle by which one pushes lightened sands their bitumens to fill the holes with excavation made by the machinery. The goal is to recreate the territory devastated after the extractions. However this waste water is extremely toxic, it contains any kind of products such of metals traces and of solvents of methane, benzene, xylene and other hydrocarbons, it is a kind of pulp of hazardous substances. One can understand that the quality of these new grounds created leaves something to be desired when one knows what they contain. With time there will be accumulation of this waste in these particular grounds, one does not know their real concentration today nor the rate/rhythm to which they pile up, because there is no independent analysis which was made. Moreover, no geological follow-up is envisaged, even if toxicity is increasing. The risk is that pollution is dawning one left the sediments and the ecosystems for then settling in the ground water because several harmful agents are not degraded easily in nature.

For the analytical aspect of the ground, if one would like to know the degree of toxicity of this one out of hydrocarbons, one proceeds initially with a sampling. The desired results will be directly influenced by the quality of the sample taken. The characteristics of the ground change much from one place to another even if the ground to be analyzed is small. In the same way, the depth should not be neglected where one will seek, it is moreover necessary to take into account the porosity and the type of ground. One can cure all these factors by taking various samples in varied places and mixing them all together. The result obtained will be a kind of average. In the sampling, one can use an organic vapor detector (DVO) which would be used for better locating on the ground the contaminated zones. Because these detectors cannot give quantitative measurements, the analyzes in laboratory nevertheless remain necessary. There is also a procedure to follow with regard to materials and techniques used for the catch of ground. It is advised to wear clean gloves and to change them after each catch and for the material, they should be out of stainless steel or Teflon. To make sure that the results obtained are valid and representative, a checking routine as of quality assurance must be formatted. The definition of Canada Environment known as: “the quality control is the whole of the procedures used to measure and, if need be, to correct the quality of the data. The quality assurance is the whole of procedures used to provide a documentary insurance of the correct application of control and quality of the data which result from this. ” To be able to obtain this control, of the stages must be followed. Among those most important is to work out a protocol, a detailed description of all that must be made. The protocol must contain, amongst other things, the methods of collection, the places, the number of samplings to be collected, the instructions of conservation, the plan of transport etc… A sample must be also taken to know the normal degree of chemicals in a clean ground in order to allow a comparison. It will then be necessary to carry out the catch of a site of control. This last must have the same pedological aspects as the contaminated site. It must as be in the vicinity and the same level in height as the corrupted place.

For the quantification of the pollutants such as benzene and ethylbenzene m-xylene, one will use gas chromatography followed by the detector by photoionization. This technique is among simplest into analytical, which showed its effectiveness through the years in the field.

Before being put in analysis in the chromatograph, the sample will have to undergo the purging and trap door. “Purging and trap” is a method which is used to recover 100% of the analytes taken in a sample (e.g. ground) for then introducing them in volatile form into the apparatus with CG.

See too

Syncrude Canada, the largest producer of synthetic oil in Canada

External bonds

production of synthetic crude oil in 2004 according to Statistical Canada
Museum of bituminous sands, site of the government of Alberta
daN Woynillowicz and Al , Oil Sands Fever: The environmental implications off Canada' S oil sands rush , Drayton Valley (Alberta), The Pembina Institute, 2005,84p.
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