Feature | Algerian Shale Gas (Part 1): Facts about shale gas and hydraulic fracturing

Publié: 2 juin 2014 dans actualité
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By Abdessalem Bouferrouk*

Despite ongoing global interest in renewable energy over recent years, shale gas has recently grabbed the headlines as a competing ‘new’ source of energy. Some have referred to it as the ‘energy bullet’ that could potentially create an energy boom in many countries such as China, Argentina, and Algeria. Indeed, the move towards exploring shale gas has intensified following the seemingly successful exploitation of the resource in the United States since the year 2000. Extraction of shale gas in the US has transformed the energy landscape in the country with shale gas accounting for 20% of US natural gas production in 2010 [1], and is expected to increase. Nevertheless, the potential of shale gas exploration has led to much debate that tends to create more heat and less light [2], often between two polarised opinions of supporters and opponents.

Figure 1: Extraction of shale gas in the USA: (a) projections [3].

What is shale gas?

Shale is a common sedimentary rock. Finely grained and soft, it is usually made of very compact layers of mud or clay in addition to fine mineral particles such as quartz and feldspar [5]. Some types of shale contain organic material making them an important source of naturally occurring gas. Shale gas is therefore another form of natural gas (NG), but it is categorised under ‘unconventional’ sources. Conventional natural gas collects in porous rocks (typically sandstones) and flows like a liquid through these pores [5]. In this case, gas can be easily extracted by drilling a vertical well into the gas pockets. Unconventional gas, however, remains trapped and scattered in millions of very tiny pores in tighter rocks.

Extraction of shale gas in the USA: extraction at the Marcellus basin [4].

The mixture of gases trapped within layers of shale may include methane, ethane, propane, butane, as well as trace quantities of argon, helium, neon and xenon [5]. Methane, the largest constituent of shale gas, is a known fuel used for household heating, cooking, power and steam generation, as well as in transportation in the form of compressed natural gas (CNG). Shale may also contain crude oil as an additional naturally occurring source of energy.

The first shale gas well was ‘fracked’ in 1947 in the USA. However, the difficulty to extract gas from hard shale formations in addition to unfavourable federal tax credits made shale gas extraction uneconomic and played a crucial role in delaying large-scale commercial production. This remained the case till the year 2000 where shale gas accounted for a mere 1 % of all natural gas production in the USA – compare this with 20% in 2010, and a predicted share of 46% of all natural gas supply by 2035 [6] (see Figure 1a). No wonder then that many countries are following in the footsteps of the USA.

A recent assessment of technically recoverable shale oil conducted by the Energy Information Administration (EIA) and US Geographical Survey (USGS) showed that the world had approximately 345 billion barrels in 2013 [7]. There are different shale formations including the Burgess shale (Canada), the Bowland shale in the north of England, the Barnett shale in Texas, and the Mercellus shale in the Appalachians (USA). All types of shale have one thing in common: tiny gaps between their particles provide pockets where both oil and gas can sit undisturbed for millions of years.

Why the recent rush towards shale gas?

Simply because of its sheer abundance, it seems. According to the British Geological Survey, the world’s shale gas reserve has recently been estimated at 450,000 billion m3 [8]. Of this, 150 billion m3 (0.033% of world total) are found in the UK, amounting to about half of its more conventional reserves [8]. Anxious about the next developments to support increasing energy demands, some governments have been busy revisiting their national energy plans in light of these findings. For instance, China (a significant consumer of coal) has seriously started looking into the option of shale gas. Figure 2 shows recent estimates of shale gas potential in a number of countries. China sits at the top with the highest recoverable potential.

Figure 2: Estimated shale gas resources in some countries [1].

China is a leading energy consumer and shale gas can present a fantastic opportunity for the country to reduce its dependency on dirty coal, thereby helping to alleviate the environmental and health problems associated with pollution from industrial power plants (in 2007, 16 out of 20 most polluted cities were in China). Global estimates may vary depending on the source of information, however. As shown in Figure 2, the estimated global shale gas reserve (as of 2013) is in the region of 207 trillion m3, of which Algeria has about 20 trillion m3 (approximately 10% of global reserve). Algeria is therefore a key contributor to hydrocarbon energy from shale, and it is thus appropriate to consider Algeria as a serious case study for shale gas development.

Extraction of shale gas

Extraction of shale gas occurs through a process known as hydraulic fracturing, or fracking for short. The fracking technique generally involves: 1) drilling and creating wells deep down below earth, 2) injecting large amounts of fluid, at high pressures, to fracture the rock (the fracking fluid is ~95-98% water plus sand and chemicals), and 3) extracting the gas (and oil). At the moment, this technique is only fully mature in the USA.

Figure 3: Hydro fracturing (fracking) to release shale gas [4].

Figure 3 shows a schematic of the processes involved in the extraction of shale gas at a typical production plant. A key stage of shale gas extraction is the horizontal fracturing of shale rocks with the fluid (step 1). This has been the most significant, recently introduced, technology as opposed to the old vertical drilling and direct extraction of conventional gas. After drilling a well down to 1,000s of meters (large-scale production uses multiple wells), the process then turns horizontally and can extend up to about 2km. High pressure mixed fluid breaks up the highly impermeable shale formations while the sand sustains the wells. After fracturing, gas and oil escape via a central pipe where they are collected for use. For a typical production plant – such as in the Mercelus Shale in the USA – 5 to 10 million gallons of water are consumed per well in a single extraction [9]. As shown in Figure 3, shale gas typically resides at much greater depths (1000s of meters) compared with conventional gas (typically at 100s of meters). Additionally, there may be underground water aquifers within shale gas extraction basins: for instance in Figure 3 underground water is protected from shale gas by an impermeable layer of seal rock.

Opportunities and challenges of shale gas

Supporters view shale gas as just another naturally available resource, much like conventional gas; after all, conventional gas has been used since the 1950s to provide clean electricity and heating at homes and businesses and has played an important role in improving comfort and quality of life. In the same way, unconventional shale gas could sustain such high level of living in ways that renewable energies cannot do in the short to medium terms. Prof. Mackay from the University of Warwick estimated that if wind power were to provide energy needs for the UK at its current rate, almost half the land would need to be covered with wind turbines [10]. Shale gas plants produce much more energy per land area, and can take place in isolated regions away from densely populated regions – though of course currently isolated regions could become more populated in the future.

Shale gas is also seen as a cleaner alternative to coal since the latter produces more soot, radioactive ash, sulphur dioxide, and oxides of nitrogen. According to some reports, the emissions due to carbon dioxide have fallen in the USA since it embraced shale gas, especially beyond 2005 [1]. This is because the carbon emission intensity of shale gas per electricity unit is less than that of coal [11]; the latter was intensively used for electricity generation in the USA prior to the year 2000. Unfortunately, this argument may not necessarily hold because reduction in shale gas prices due to high volume production would ultimately lead to increased energy consumption (similar to what has occurred in the USA), resulting in increased levels of harmful emissions and undesirable climatic changes. One must also consider that the USA has been shipping large amounts of coal to Europe and Asia (especially China) following its shale gas boom, so the emission effects on a global scale are not actually reduced.

Exploration of shale gas offers some level of energy security as well as additional income for nations. Despite public opposition, shale gas could be seen as a welcome addition to the ‘energy mix’ for countries currently importing gas such as the UK, partly because it would relieve some burden during energy peak demands, and could lead to lower energy bills like it did in the USA. Further, shale gas exploration will lead to job creation and reduction in unemployment. In an age where geoengineering is seen as key force that will shape the 21st century, the timely exploitation of shale gas would allow for the transfer of engineering skills from traditional mining activities to large-scale shale gas projects.

Fracking activities may also create an economic boom for surrounding towns and cities. A good example is that of Hassi Messoud in the south of Algeria, which has grown in size and economic status due in part to large-scale extraction of hydrocarbons and associated economic incentives for workers and their families. In the USA, one can own the gas that is beneath their land, so shale gas can make some people very rich, just like those who currently earn substantial income renting their private land for solar and wind turbine installations.

For opponents of shale gas, it is seen as another fossil fuel that releases harmful emissions. Given global moves towards mitigating the effects of climate change due to hydrocarbons, starting shale gas developments would hinder such initiatives. People are concerned whether we ought to invest in yet another carbon-based economy since this might decelerate development of renewable energy programs worldwide. It is not true the world will run out of energy as such, but quite the opposite. If technical ingenuity and political will combine, solar energy alone can resolve most of our energy problems.

There is serious concern regarding the contamination of fresh water by toxic chemicals that might leak into the surrounding land after fracking. In the USA, people near extraction sites have complained about drinking water making them feel ill [12]. For example, a badly managed fracking site has caused contamination of ground water in Wyoming, USA, revealing one ugly reality of the shale gas industry [8]. A research team led by Prof. Jackson from the Duke University in Durham, North Carolina, analysed samples of water from an area about 1km away from the large Marcellus fracking site and discovered that water at these locations contained 17 times more methane compared with water from farther locations [13]. Shale gas is typically composed of over 90% methane. Migration of methane to nearby private drinking water resources is a major concern with natural gas extraction in general. Methane is not regulated because it does not affect our ability to drink water – it does not affect its colour, smell or taste – but it can be a serious explosion hazard especially in confined spaces when moving from water to air. In the extreme case, methane can also pose a serious asphyxiation hazard [13]. Although this is alarming, the team admitted that no chemical additives could be found that can be traced back to shale at the fracking site, so this particular set of results remain inconclusive. Still, the main hazard with methane escaping into the atmosphere is that it is 25-30 times more powerful than carbon dioxide [15].

Another controversial issue is how to safely dispose of fracking water. Such water usually comes up to surface after fracking and can cause harm if not managed carefully. In West Virginia (USA), fracking wastewater disposed on an acre of land was found to cause trees and vegetation to die: according to results published in the Journal of Environmental Quality 56% of the trees had died after two years of pouring the wastewater on the area [14]. Not surprisingly, environmental scientists are worried about this problem knowing that companies may illegally dispose of fracking water. Indeed, there are reports that fracking companies have resorted to paying claimants substantial sums of money in return for them not raising health issues in the future [12]. Communities near drilling sites have also reported to only buy bottled water; even their animals do not drink from water close to fracking sites [12].

The nature of the chemicals used with high-pressure fracking fluid is also worrying. In the USA, the law does not allow fracking companies to disclose the type of chemicals used in fracking [12]. This is enforced to the extent that even if a doctor suspects a patient has health issues, e.g. breathing or lung problems due to suspected chemicals from fracking, they are not allowed to pass on such information to others [12]. It remains therefore a trade secret, effectively stopping researchers from quantifying potential risks of the chemicals.

There are also real concerns with seismic risks; though these have been found to be similar to those caused by mining activities. Some measurements have indicated that small-scale earthquakes in the USA have become quite common [12]. Although these are not immediately catastrophic, the fear is that such small-scale fluctuations can suddenly become dangerous due to movements in the earth’s crust layers. In 2011 for instance, tremors of magnitude 1.5 to 2.3 were felt near an exploratory site near Blackpool, UK and these were directly linked to fracking activities [1]. However, similar risks have long been associated with geothermal energy implying that both sectors ought to be managed rather carefully.

Finally, in terms of economic challenges, there is an uncertainty associated with the actual amount of gas identified but that could be more challenging to extract from suboptimal wells than otherwise suggested by initial surveys. As a result, fracking costs can rise significantly.

Part 2 will investigate the case of Algerian shale gas development in more details, looking into the opportunities and risks associated with the recent decision to go ahead with exploring shale gas.

 

References

[1] Michael Brooks, “Frack to the future”, New Scientist, 8/10/2013, Vol. 219 Issue 2929, p36. August 2013.

[2] Editorial, “The fracking debate needs more light, less heat”, New Scientist, issue 2929, August 2013.

[3] U.S Energy Information Administration, Annual Energy Outlook, June 2012.

[4] Peter Aldhous, “Fracking into the unknown”, New Scientist, 2013.

[5] Science Media Canada (SMC) Report, “Shale Gas and Fracking”, February 2012.

[6] Paul Stevens, “The Shale Gas revolution: developments and changes”, Technical Report, Chatham House, 2012.

[7] Edward McAllister and Timothy Gardner, “World has 10 times more shale gas than previously thought, says US EIA”. News Article (http://www.thegwpf.org/world-10-times-shale-oil-thought-2011-eia/), accessed May 2014.

[8] Mike Stephenson, “Frack responsibly and the risks are small”, New Scientist, Jan 2012.

[9] Katrina Korfmacher, “Introduction to Horizontal Hydro fracturing”, Department of Environmental Medicine, University of Rochester, April 10, 2013.

[10] David MacKay, “A reality check on renewables”, TEDxWarwick, March 2012. Retrieved from http://www.ted.com/talks/david_mackay_a_reality_check_on_renewables.

[11] John Broderick, and Kevin Anderson, “Has US shale gas reduced CO2 emissions?”, research briefing from Tyndall Manchester for Climate Change Research, October 2012.

[12] Ian Stewart, “Fracking: the new energy rush”, BBC Horizon, 20 Jan 2013.

[13] RB Jackson, B Rainey Pearson, SG Osborn, NR Warner, A Vengosh, “Research and policy recommendations for hydraulic fracturing and shale gas extraction”. Centre on Global Change, Duke University, Durham, NC, 2011.

[14] Adams, Mary Beth, “Land application of hydrofracturing fluids damages a deciduous forest stand in West Virginia”, Journal of Environmental Quality, Vol. 40: 1340-1344, 2011.

[15] Abdessalem Bouferrouk, and Abdelaziz Bouferrouk, “Renewable Energy Development in Algeria: Applications, Opportunities and Challenges”.  Proceedings of the First International Conference on Nanoelectronics, Communications, and Renewable Energy (ICNCRE 13), University of Djijel, Algeria, pp-420-428, 2013.

Abdessalem Bouferrouk

Dr Bouferrouk is a Senior Lecturer (Mechanical/Aerospace) at the University of West of England, Bristol, UK. Previously, he was a Lecturer and Senior Research Fellow at Exeter University. His research interests are varied ranging from field measurements of flow turbulence at wave and tidal energy sites, flow control, energy efficient systems, and renewable energy. Previously, Dr Bouferrouk worked at the universities of Birmingham and Nottingham. He holds MEng (Aerospace Engineering) and a PhD from Southampton University.

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