Sustainable Shale Gas Production is Feasible
Cheap shale gas is transforming the economy of the US. This prosperity is clouded by questions regarding the environmental risk in the gas extraction process. These risks are manageable with a combination of regulation, industry cooperation and informed local activism in areas of commercial activity.
The mechanism of shale gas formation is such that one would expect it to be found worldwide. A recent book, Shale Gas: the Promise and the Peril, describes the scientific rationale behind this belief. In fact, the US Energy Information Administration (EIA) recently issued a report in confirmation. According to the EIA the top three resource accumulations are in China, US and Argentina. But Europe has important deposits that could change the dynamics of the current dependence on Russia. A chilling reminder of this dependence was when Russia shut off the gas shut for ten days in January, 2009, reportedly to punish Ukrainian transgression. Some estimates had Slovakia losing one billion Euros as a result.
If the US shale gas exploitation experience is repeated in Europe, one would expect gas prices to drop over time. Today, European natural gas is priced at nearly three times that in the US. Some of the US gas is wet. This means it has a significant proportion of larger molecules such as ethane, propane and butane. This character will soon cause the US to be the low cost producer of ethylene derivates such as polyethylene and polyvinyl chloride (PVC). Europe could well face a similar rosy future.
The economic prosperity associated with cheap shale gas is undeniable, so the only issue for discussion in Europe is environmental risk. But in discussing risk, one must recognize that any industrial enterprise has risk. France is the most nuclear dependent nation in the world. Germany instituted a plan to phase out nuclear plants altogether following the Fukushima Daiichi disaster. These neighbors are clearly looking at nuclear risk differently. France has already imposed a moratorium on hydraulic fracturing of rock, commonly known as fracking, the key technology enabler of shale gas production. Shale Gas: the Promise and the Peril goes into considerable details regarding the risks and means to ameliorate them. Here we will briefly discuss water related issues.
Fracking involves injecting up to 20 million liters of water together with less than about 1% chemicals and some sand. Up to about a third of the water is returned to the surface after the fracking operation. This is known as flowback water. Even if fresh water were to form the basis of the fracking fluid, the flowback water would be salty. This could be ten times the salinity of sea water, which is itself about 35000 parts per million (ppm). Such water cannot be surface discharged. Even for agriculture, the limit would be about 1000 ppm. Water for human consumption is limited to 500 ppm.
Disposal of flowback water: Flowback water must be disposed of in one of only two ways. One is disposal in deep porous rock capable of accepting this fluid. In the US each such well is a closely regulated activity by the Environmental Protection Agency (EPA). If Europe followed this model, similar regulatory oversight would be required. But the geology of the area has to cooperate. On the US East Coast deep disposal is essentially not feasible in the prolific Marcellus and Utica prospects.
The other disposal method is to treat and re-use for the same fracking purpose. This is the preferred option from an environmental standpoint in part because it minimizes handling and transport, which are subject to spills. The cost of the re-use option is less if the water does not have to be treated to fresh standards of 500 ppm salinity. In recognition of this, the service industry has been innovating to permit salty water to be used as the fracking fluid base. Today, 40,000 ppm salinity is completely tolerable. One could reasonably expect that number to go to 80,000 ppm shortly. Even higher salinity tolerance targets are also technically feasible.
All this means that flowback water could re-used with minimal treatment in some cases. In other cases some fresh water could simply be added for dilution and some other steps may be needed, such as removal of bacteria. In the more difficult instances, desalination would be required, but targeting salinities of only 40,000 ppm today and even higher targets tomorrow. This limited desalination keeps the costs down. Because the water is being returned, minor impurities such as naturally occurring radioactive elements would simply be sent back down to where they came from. Were the water to be treated for discharge, high salinity and radioactivity would not be allowed. Treatment for surface discharge or other use will always be more costly than for re-use. This is another reason not to consider treatment at existing water treatment plants, even if they are modified to accept this waste.
Zero fresh water usage: If re-use of salty water is feasible, why is industry using fresh water to begin with? The answer is it ought not to be. Using brackish water unsuited to human consumption, or even for agriculture, is completely feasible. Municipal “gray water” from effluent treatment plants, or any marginally clean water, could also be used. But the best and most reliable candidate water is water from saline aquifers.
Water aquifers tend to get salty at greater depths. This is why most fresh water in the world is found at depths less than 300 meters, more often less than half that. Consequently, salt water bodies are quite prevalent in most places and have no use for human consumption or agriculture. Using salty water for fracking ensures no competition with other conventional uses. This is especially notable in years with severe drought. 2011 saw the worst drought in Europe for a century or more. Many believe that global warming is causing more frequent droughts in some countries. Whether this is the case or not, using water non competitive with other uses is a good idea. Some parts of Europe being explored for shale gas are in heavily farmed areas. In these cases especially, not competing for irrigation water would be good policy.
Low-cost energy is a tide that lifts all boats of economic prosperity. Shale gas is a powerful such tide. It has burst upon us so suddenly that we have been startled by the debris it carried with it. This debris is manageable, allowing us to enjoy the benefits of the tide.
Vikram Rao is Executive Director of the Research Triangle Energy Consortium. Mr. Rao spent more than 30 years with Halliburton, most recently serving as Senior Vice President and Chief Technology Officer, responsible for the company’s technology effort as well as intellectual asset management. His sbook Shale Gas: the Promise and the Peril, was recently published by RTI Press