The Environmental Performance Of Canadian Oil Sands

The Environmental Performance Of Canadian Oil Sands

Introduction

Oil sands refer to loose sand deposits containing highly viscous petroleum known as bitumen. Oil sands are constituted of a mixture of sand, clay, water and bitumen oil, which are situated in the Northeastern Alberta in Canada, which include Athabasca, Cold Lake and Peace River. The oil sand deposits in Canada are the largest in the world, contributing to over 10% of the world’s oil reserves. (Berkowitz &Speight,1975).

Conventional crude oil, on the other hand, refers to a liquid petroleum that is pumped from underground. It varies widely in terms of sulfur content, viscosity and density. It is either classified as light, medium or heavy, which is the oils relative density based on API gravity. While crude oil can be pumped from the deposits underground as it flows, oil sand is too thick and doesn’t flow; hence it cannot be pumped from the ground(Berkowitz &Speight,1975). Instead, it is mined through the injection of Steam into the well, which heats it first.

Several methods are used in the extraction of oil sands. Examples of these methods include surface mining, primary production, tailing ponds, vapor extraction and many others. Some of these methods of extracting oil are recent ones, while others have been in use from the past. These methods have various strengths and limitations which determines their efficiency and suitability for use in mining of oil sands. The following discussion will give a description of these various methods while considering their cost effectiveness and environmental impacts..

Methods Of Extracting Oil Sands

1.Surface mining

This method is used when the deposits of oil sands are nearer to the surface , lying within a range of 70 metres from the earth’s surface. It involves the use of large shovels for scooping oil sand into the haul tracks, which then transport it to the crushers where huge clumps of oil sand get broken down. Oil sand then gets mixed with hot water to form a slurry, after which it is pumped via pipeline to a plant referred to as an upgrader. (Schramm et al,2000). In the upgrader, bitumen gets separated from other components like clay, sand and water.

This method is very uneconomical for oil deposits, which occur deeper below the ground beyond 70 metres. This method also involves clearance of large tracts of land hence interfering with biodiversity like the vegetation and living creatures in a place. (Naeth et al,2011). It is also accompanied by the production of large amounts of Nitrogen oxides which are major environmental pollutants.

2.Tailing ponds

They are present in all types of surface mining. Tailing ponds are dam and dyke systems containing suspended solids, salts and other chemicals such as benzene, hydrocarbons, naphthenic acids and even fine silts.(Schramm et al,2000). Tailings constituted of water,clay,sand and traces of oil from the oil sands get pumped to ponds .In the ponds, both sand and clay settle at the bottom  and the water at the top gets reused for mining and in bitumen separation. A tailing pond gets reclaimed once it stops being useful. Huge volumes of tailings remain as byproducts of surface mining. The tailings get filled with water hence becoming toxic to the wildlife around(Schramm et al,2000). This is a major environmental problem faced by the oil industry. It is also very costly to reclaim the tailing ponds as it involves the removal of the tailings.

3.Steam-assisted Gravity Drainage (SAGD)

This method involves using two wells, which are the production well and the injection well in recovering bitumen. The injection well gets drilled vertically through the deposit, after which it is turned at 90 degrees and then drilled horizontally. The production well is then drilled deeper compared to the injection well and it is parallel to the horizontal part of the injection well.(Giacchetta et al,2015). Steam then gets injected through the deposit via the upper well. Heated bitumen then starts moving by gravity towards the production well. Pumps in the production well assists to draw bitumen from inside it onto the surface.

This method is more efficient than the other in-situ methods as it involves the reduction in the use of both water and even natural gas, reduced carbon dioxide emissions and the increased recovery of bitumen when technological advancements are used in extraction(Lightbown,2016). This method is also deemed to be cheaper than CSS as it facilitates higher production of oil and recovering of approximately 60% of oil in a particular place.(Giacchetta et al,2015). Lastly, it is an economically feasible method that can be applied in a large area of oil sands

However, since this method involves drilling of wells, it has impacts on various infrastructure such as roads, powerlines, pipelines etc. It therefore leads to the degradation of the environment by causing fragmentation of forests hence disconnecting the reserves which can even displace wildlife. Its effects on land in the environment is therefore larger than those of surface mining. Moreover, SAGD is an environmental threat when it comes to the release of greenhouse gases and Sulphur dioxide which is a serious environmental pollutant, causing acid rains.

4.Cyclic Steam Stimulation (CSS)

This method involves pumping Steam downwards through a vertical well so as to liquefy or soak the bitumen. The bitumen then gets pumped onto the surface via the same well and the process gets repeated until majority of oil reserves is removed. This method is recognized by its quick earlier production of oil sand. However, it has a lower recovery of oil compared to SAGD which ranges from 10%-40% of the oil in a place.

5.Cold Heavy oil Production with Sand (CHOPS)/Primary production

CHOPS is a method used to extract very difficult and heavy crude oil with an API gravity below 20. Sand influx is deliberately initiated in the completion procedure thereby increasing the reservoir’s permeability hence allowing the flow of heavy oil.(Kuhlman,2014).  Sand is used to enhance the productivity of the oil well. This method of oil sand extraction has been proved to be more economical as compared to the others because it doesn’t need expansive tools or chemicals for enhancing the production rates. It doesn’t also need much technological advancement .Compared to the thermal recovery methods ,this non- thermal recovery method has an added  advantage  due its simultaneous production of both oil and sand.

The following are some of the features of CHOPS method in comparison to other recovery methods:

a). It involves the  use of natural energy from the reservoir formation which assists in decreasing the cost of recovery hence improving profit earned.

b). It has Progressive cavity pumps for the simultaneous pumping of both oil and sand

c). High production rate is enhanced by the formation of wormholes.

6.Toe to Heel Air Injection (THAI)

This refers to a new experimental method which combines both the vertical air injection and the horizontal production well .Oil gets  ignited in the reservoirs hence creating a vertical wall of fire to move from the toe of the horizontal well to the heel of the well hence burning the heavy components of oil and upgrading a portion of the heavy bitumen to a lighter oil.(Paes & Throckmorton, 2008)

This method has a disadvantage in that at times, projects involving fireflood have not performed well due to the difficulty to control an outbreak of flames which can set the wells on fire. Some oil companies,however do feel that this method does not need energy for generating Steam. Moreover, they argue that it consumes less amount of freshwater for extraction and generates 50% lower amount of greenhouse gases compared to SAGD.They therefore consider it more preferable to other methods of extraction.(Paes & Throckmorton, 2008).

From the above discussion of the above methods of oil  sand extraction,it is very convincing that CHOPS  method is the most favourable owing to the various advantages attached to it including its utilization of natural of energy,simultaneous production of oil and sand  and its economical nature in production.

Methods Of Oil Sand Extraction In Venezuela

In Venezuela, oil sands have a lower viscosity compared to the ones in Canada hence allows the application of the conventional drilling methods for example CHOPS (primary extraction) methods. This method involves drilling of long horizontal wells followed by a great number of multi-lateral branches.(Kuhlman,2014).  . The main well and the sub branches are strategically situated in the best parts of the oil reserves by using a combination of several factors such as seismic data, geophysical log data and measurements during drilling. The Steam based in situ production method is also used to extract oil in Venezuela.

Differences Between The Oil Sand Locations Of Canada

The Athabasca Oil reserves makes the greatest oil reserves in Canada and even in the world with 150 billion barrels of oil. In Athabasca, the oil sand deposits are shallowly located so that it is easy to use the method of surface mining in the extraction(Berkowitz &Speight,1975). Moreover, surface mining method becomes more efficient to apply because the oil sands have large quantities of bitumen which are covered by an overburden material. Bitumen in Athabasca has very high viscosity and usually denser than water.

The oil deposit in Cold lake is situated at 300 km to the northeast of Edmonton, covering an area of 6500km2.It is second to the Athabasca oil deposits in terms of size in Canada. It has 60-125 billion barrels of the heavy oil. Oil in Cold lake is of low gravity, higher viscosity and stagnant inside the reservoir. Reserves of oil are fluidic and can get extracted using conventional methods. The bitumen in Cold lake contains more alkanes and lesser asphaltenes compared to the ones in the 2 Alberta oil sands.(Brooks,1988).CSS method is the method dominantly used for production of oil sands due to the fluidity of Cold lake bitumen. The depth of deposits lies within (400-600) meters hence too deep to mine by surface methods.Lastly,oil in Cold lake is less suphurous

Peace river oil sand is situated in the Northwest-central of Alberta. It is the least of the 3 major oil sands in Canada. The deposits of oil sands have a thickness range of 5 to 25 metres. The oil deposits are located very deeply hence have to be exploited through insitu methods such as SAGD and CHOPS. It produces 30 billion barrels of oil reserves .(Spreight,2012).

References

Kuhlman, M. I., & Ware, C. H. (2014). U.S. Patent No. 8,899,327. Washington, DC: U.S. Patent and Trademark Office.

Brooks, P. W., Fowler, M. G., & Macqueen, R. W. (1988). Biological marker and conventional organic geochemistry of oil sands/heavy oils, Western Canada Basin. Organic geochemistry, 12(6), 519-538.

Speight, J. G. (2012). Oil sand production processes. Gulf Professional Publishing.

Paes, R., & Throckmorton, M. (2008, June). An overview of Canadian oil sand mega projects. In 2008 5th Petroleum and Chemical Industry Conference Europe-Electrical and Instrumentation Applications (pp. 1-9). IEEE.

Giacchetta, G., Leporini, M., & Marchetti, B. (2015). Economic and environmental analysis of a Steam Assisted Gravity Drainage (SAGD) facility for oil recovery from Canadian oil sands. Applied Energy, 142, 1-9.

Schramm, L. L., Stasiuk, E. N., & MacKinnon, M. (2000). Surfactants in Athabasca oil sands slurry conditioning, flotation recovery, and tailings processes (pp. 365-430). Cambridge University Press: Cambridge.

McPherson, E. G., Chute, F. S., & Vermeulen, F. E. (1986). The Electromagnetic Flooding Process for In-Situ recovery of Oil from Athabasca Oil Sand. Journal of microwave power and electromagnetic energy, 21(3), 129-147.

Berkowitz, N., & Speight, J. G. (1975). The oil sands of Alberta. Fuel, 54(3), 138-149.(Berkowitz &Speight,1975)

Naeth, M. A., Chanasyk, D. S., & Burgers, T. D. (2011). Vegetation and soil water interactions on a tailings sand storage facility in the Athabasca oil sands region of Alberta Canada. Physics and Chemistry of the Earth, Parts A/B/C, 36(1-4), 19-30.

Lightbown, V. (2015). New SAGD technologies show promise in reducing environmental impact of oil sand production. Journal of Environmental Solutions for Oil, Gas, and Mining, 1(1), 47-58.