With European energy security draining away, any discussion about our energy future should begin with energy security, price and a rounded assessment of the impact that new energy supplies may have upon our environment. European primary energy production peaked at 1136 million tonnes oil equivalent (mmtoe) in 1997 and has since fallen 15% to 970 mmtoe in 2012. It is against this backdrop that many European governments are now embracing The American Dream in promoting shale gas as the cheap, clean, abundant and secure “bridging fuel” to a carbon free energy future. None of this is true.
Shale gas is not cheap, it’s certainly not clean and in geological terms it is a low-grade resource. Any country going down this route is also making a commitment to drill hundreds to thousands of new wells every year to keep the gas flowing. So where does the truth really lie? In part 1 of 2, I describe what shale gas is and consider environmental factors such as intensity of development, potential contamination of ground water and CO2 emissions. Part 2 will consider economics and shale gas potential of the UK.
Figure 1 The Northwest corner of Bradford County in Pennsylvania USA . This is a production sweet spot in the prolific Marcellus Shale. Mixed arable land with forest close to the Appalachian Mountains, not too dissimilar to parts of rural England and Europe. How many shale gas drilling pads and production wells can you see in the image? What impact does this have on a landscape already overprinted by Man’s roads, farms, towns and quarries? Click on all images to get a large version that opens in a new browser window.
The energy debate
With energy prices rising once again and frost creeping under the doors of many pensioner’s homes in Scotland, politicians are blaming everyone but themselves for our energy plight. In trying to reach any sensible conclusion in a discussion about our energy future, it is important to understand our energy past. Since the middle of the 19th century growing supplies of cheap fossil fuels (first coal, then coal+oil and then coal+oil+natural gas) powered industrial society enabling the global population to explode to 7 billion souls (Figure 2). This era is coming to an end. Not because of climate change but because we are running scarce of cheap fossil fuel. Hence the great interest in the alternative to cheap fossil fuel i.e. expensive fossil fuel, i.e. shale oil and gas. Cheap fossil fuels brought society a myriad of benefits that we have all come to take for granted (Figure 2). Society is going to have to accept that any effort to replace cheap fossil fuels with alternatives, be it wind power, nuclear power or expensive fossil fuels means there are going to be costs associated with those benefits. These costs come in the way of higher energy bills, inconvenience and environmental degradation. The choice is between accepting these costs and having the lights on at Christmas or not. The energy debate is multi-dimensional, and so there is no right answer. Only a choice between a number of poor options.
Figure 2 In the 18th century, Europeans were running out of wood to burn. And then along came coal, the steam engine and before we knew it, Porsches, iPhones and holidays in Spain. The wealth created by consuming fossil fuels has underpinned the explosion of global population by providing food and amazing advances in medicine such as the eradication of smallpox that killed 300 to 500 million people in the 20th Century. Society would do extremely well to not forget the stunning benefits that coal, oil and gas has provided.
What is shale gas?
Conventional oil and gas is formed at a depth of approximately 3000 m (10,000 ft) when mudstones (shale) rich in organic matter (the source rock) are heated to about 100˚C and squeezed by burial to produce first oil and then gas as burial and temperatures rise. If the organic content is high, so much oil and gas are produced in the mudstone that it creates natural fracture pathways and escapes. Being lighter than water it floats upwards where some is trapped in either sandstone or limestone reservoirs (that act like sponges) that we commonly know as oil and gas fields. These are super-concentrated accumulations of energy (Figure 3).
In shale gas and shale oil, the organic content of the shale is lower and the gas and oil that is formed by the same processes remains trapped in the shale. These are low grade concentrations of energy distributed through vast volumes of rock. The gas and oil does not escape because the shale is “impermeable”, that is it lacks connected holes big enough to allow fluids to flow through it. The drain in a shower is permeable. A drain covered in hair is not. A sieve is permeable. A sieve clogged with starch after straining rice is not.
Since shale is impermeable and has not given up its gas and oil for millions of years Man has invented a way of making it permeable, namely hydraulic fracturing (fracking). In fracking, a fracking fluid is pumped into the well at extreme high pressure so that the pressure in the well exceeds the confining pressure of the rock which then fractures, enabling the gas or oil to flow. This is tantamount to “blowing up the rock” deep down in the Earth’s crust. But that is only part of the story. Fracking shale only really works in long horizontal wells drilled along “sweet spot” horizons (Figure 3), where multiple fracking events may be conducted. Drilling long horizontal wells and conducting multiple fracks costs a lot of money and energy. How on Earth can shale gas be cheap?
Figure 3 From the US Energy Information Agency. Pools of conventional oil and gas flow freely to the surface whilst in shale the well is drilled along the gas rich zone and fracking shatters the rock to enable some of the trapped gas to flow into the well bore.
Intensity of development
Of the various environmental impacts discussed below, it is the intensity of shale developments, should they go ahead, that may give reason for concern. In the USA good wells tend to produce between 2 and 5 million cubic feet per day at the start, declining to around 1 million cubic feet per day per well after 2 or 3 years. A universal feature is high decline rates, typically 40% in the first year and 20 to 30% in subsequent years . This means that once you jump on the shale carousel you have to keep drilling to maintain or grow production – lots and lots of wells every year.
To place this in context, the UK currently consumes about 8000 million cubic feet of gas per day  and so to provide all of our gas needs from shale would require about 8000 wells.
On average fracking a well requires 1000 truck trips to transport material from and to the well site (email correspondence from a US Oil company CEO)
Another way to place this in context is to compare shale production with large conventional off shore gas fields. Initial flow rates from the Ormen Lange gas field in Norway were of the order 350 million cubic feet per day per well . Initial production from the Marcellus shale of Bradford County is typically 4 million cubic feet per day per well. Thus around 88 shale wells may be required to replace a single offshore well.
Of course, if it was easy to find large new offshore gas fields in Europe then we wouldn’t be contemplating shale, but we can’t. Most of the large European oil and gas fields have already been found and the reserves used up. And of course, drilling shale onshore dispenses with the need for massive offshore structures and sub-sea pipelines.
The intensity of development should really only be of concern during drilling operations. In Bradford Co Pennsylvania, well spacings are typically 1 to 2 km (Figure 4). And so a neighbourhood may be inconvenienced for a few months while a well is being drilled, but then the drill crew packs up and moves on leaving a clean and tidy drill pad with a well head. But the drill crews may return at some future date to re-frack the well.
Figure 4 Vertical view of Figure 1. I count 9 shale wells, some with tailing ponds. The landscape is already 100% overprinted by Man and once the rigs are gone, the visual impact of the drill pads should not be too significant.
Gas wells also need to be connected to a processing plant by pipelines that will inevitably result in more disruption during the construction phase. The processing plant will take the form of a mini petrochemicals complex where ethane and longer chain hydrocarbons are removed and used by the petrochemicals industry and impurities like N2 and CO2 are removed and most probably vented.
The scale of shale drilling operations in the USA has been phenomenal. The shale miracle has been brought about by application of sheer American muscle. There are currently 1685 land rigs drilling in the USA (source Baker Hughes). In the UK in October there were 2 land rigs drilling and 34 land rigs in the whole of Europe (excluding Turkey). If the UK and Europe are to emulate the USA then there will need to be an enormous up-scaling of onshore drilling equipment and materials and the accompanying supply chains. All this of course would be extremely good news for employment in the heavy industry sector.
Ground water contamination
The most commonly voiced concern about shale drilling and fracking operations is contamination of ground water by the fracking fluid. The Royal Academy of Engineering has conducted a comprehensive review of this and say the following :
Concerns have been raised about the risk of fractures propagating from shale formations to reach overlying aquifers. The available evidence indicates that this risk is very low provided that shale gas extraction takes place at depths of many hundreds of metres or several kilometres. Geological mechanisms constrain the distances that fractures may propagate vertically. Even if communication with overlying aquifers were possible, suitable pressure conditions would still be necessary for contaminants to flow through fractures. More likely causes of possible environmental contamination include faulty wells, and leaks and spills associated with surface operations. Neither cause is unique to shale gas. Both are common to all oil and gas wells and extractive activities.
Of all the potential environmental risks associated with drilling shale, the risk to contamination of ground water can be reduced to extremely low levels.
Drilling a well also produces a large volume of drill cuttings (the smashed up rock), drilling mud and frackng fluid. Once the well is fracked, the fluid must be removed to allow the gas to flow. The drilling mud and fluids can become contaminated with heavy metals and naturally occurring radioactive isotopes. If large-scale shale drilling operations were to proceed, any government will require a plan for disposal of these by-products of the drilling process.
One of the biggest myths associated with shale gas is the notion that it can help reduce CO2 emissions. Burning natural gas instead of coal today can certainly reduce the rate of CO2 emissions (Figure 5). But this is only of any value to the greenhouse gas content of the atmosphere if the coal not burned today is never burned. Of course once we run out of gas to burn we will turn back to coal. The US is currently crowing about the reduction in CO2 intensity of its economy stemming from the shale revolution, but much of the coal not burned in the USA has simply been exported and burned else where, amongst other places in Britain.
Figure 5 A comparison of the CO2 intensity of various generating technologies by David MacKay . In natural gas it is C-H bonds that are broken when the gas is combusted to form CO2 + H2O. In coal, it is mainly C-C bonds that are broken when it is combusted to form CO2 + CO2. Hence the much higher CO2 intensity of coal. A country can reduce its rate of CO2 emissions by substituting gas for coal fired power but attacking the shale gas wedge of the resource pyramid will simply mean the burning of more gas long-term that will ultimately mean higher not lower CO2 emissions.
The real emissions concern with shale gas should focus on the gigantic size of the resource should it be exploited globally (Figure 6). We are beginning to attack a new slice of the resource pyramid. Any government, genuinely concerned about long-term emissions scenarios would quite simply ban shale gas operations.
Figure 6 This estimate of global recoverable shale gas from the BGS  contains 6318 trillion cubic feet (tcf). According to BP  global gas reserves currently stand at 6545 tcf of mainly conventional reserves. Developing shale will effectively double CO2 emissions from natural gas and not reduce them.
In part 2 I will take a cursory look at the economics of shale and explain why Rex Tillerson CEO of ExxonMobil is losing his shirt. I will also take a look at potential shale gas developments in the UK and attempt to summarise the many facets of the shale gas debate.
1. 2013 BP statistical review of world energy
2. Marcellus shale gas Bradford Co Pennsylvania: production history and declines
3. Norsk Hydro Tests First Ormen Lange Gas Production Well
4. Shale gas extraction in the UK: a review of hydraulic fracturing June 2012
5. Potential Greenhouse Gas Emissions Associated with Shale Gas Extraction and Use
6. The Carboniferous Bowland Shale gas study: geology and resource estimation