Monday, 18 December 2017

Small Earthquakes at Fracking Sites May Be Early Indicators of Bigger Tremors

7 fears about fracking: science or fiction?

The extraction of shale gas with fracking or hydraulic fracturing has revolutionized the production of energy in the United States, but this controversial technology, banned in France and New York State, continues to generate criticism and protests.

The detractors of the technique, which consists of injecting water and chemical additives at high pressure to fracture the rock containing the hydrocarbons, warn about the possible contamination of water, methane leaks and earthquakes, among other risks.

The British Royal Academy of Sciences, the Royal Society, said in its 2012 report that risks can be effectively managed in the UK "as long as the best operational practices are implemented," Richard Selley, professor at the University of Emeritus of Imperial College in London and one of the authors of the report.

But others, who have contrary opinions, are equal of strict. For example, regarding the possibility that fracking poses a risk of methane leakage, William Ellsworth, a professor of geophysics at Stanford’s School of Earth, Energy & Environmental Sciences. It is not a matter of determining if the wells may have leaks, but the question must be, what percentage has leaks.

In the middle of an intense and growing controversy about fracking, Stangford University Researchers investigated what science says up to now.

Can it cause earthquakes?

Two of them occurred in 2011 in England and led to the temporary suspension of the exploration with fracking.

The first, which occurred in April of that year, near the city of Blackpool, reached 2.3 on the Richter scale and was registered shortly after the company Cuadrilla used hydraulic fracturing in a well.

On May 27, after resumption of fracturing in the same well, seismicity of 1.5 was recorded.

The network of monitors of the British Geological Society, BGS, captured both events, which were not felt by the local inhabitants.

The company Cuadrilla and the government commissioned separate studies.

"Both reports attribute the seismic events to the fracturing operations of Cuadrilla," said the Royal Society, the British Academy of Sciences, in its joint report with the Royal Academy of Engineers on hydraulic fracturing, published in 2012.

Earthquakes can be unleashed mainly by high pressure injection of wastewater or when the fracturing process encounters a fault that was already under stress. However, the Royal Society said that activities such as coal mining also produce micro-organisms. The suspension of fracking in the United Kingdom was lifted in December 2012, following the report of the Royal Society, which ensured that fracking can be safe "provided that the best operational practices are implemented.

In the United States, a study published in March 2013 in the journal Geology linked the injection of wastewater with the 5.7 magnitude earthquake in 2011 in Prague, Oklahoma. The wastewater injection operations referred to in the study were conventional oil exploitation. However, seismologist Austin Holland of the Oklahoma Geological Survey said that while the study showed a potential link between earthquakes and wastewater injection, "it is still the opinion of the Oklahoma Geological Survey that those tremors could have occurred naturally."

Another study published in July 2013 in the journal Science and led by Nicholas van der Elst, a researcher at Columbia University, found that powerful earthquakes thousands of kilometers away can trigger minor seismic events near wastewater injection wells.

The study indicated that seismic waves unleashed by the 8.8 earthquake in Maule, Chile, in February 2010, moved across the planet causing tremors in Prague, Oklahoma, where the Wilzetta oilfield is located.

"The fluids in the injection of sewage into wells are bringing existing faults to their limit point," said Van der Elst.

Can fracking contaminate the water?

At the request of the US Congress, the Environmental Protection Agency of that country, Environmental Protection Agency, EPA, is conducting a study on the potential impacts of hydraulic fracturing on water sources for human consumption.

A final draft of the report will be released at the end of 2014 to receive comments and peer review. The final report "will probably be finalized in 2016," the EPA confirmed.

In 2011, Stephen Osborn and colleagues at Duke University published a study in the journal of the US Academy of Sciences, according to which the researchers detected contamination of methane water sources near fracking exploration sites in the Marcellus formation. in Pennsylvania and New York.

The study did not find, however, evidence of contamination by chemical additives or the presence of high salinity wastewater in the fluid that returns to the surface along with the gas.

For its part, the Royal Society, the British Academy of Sciences, said that the risk of fractures caused during fracking reaching the aquifers is low, as long as gas extraction takes place at depths of hundreds of meters or several kilometers and wells and the tubing and cementing process are built according to certain standards.

A case cited by the Royal Society in its 2012 report is that of the town of Pavillion, Wyoming, where fracking caused the contamination of water sources for consumption, according to an EPA study. Methane pollution was attributed in this case to poor construction standards and shallow depth of the well, at 372 meters. The study was the first of the EPA to publicly link hydraulic fracturing with water pollution.

However, as in the Duke University study, there were no cases of contamination by the chemical additives used in hydraulic fracturing.

We must remember that when a well is drilled and the aquifer area is crossed, three steel rings are placed, surrounded by cement, below the aquifer.

How to control the use of chemical additives?

Trevor Penning, head of the toxicology center at the University of Pennsylvania recently urged the creation of a working group on the impact of fracking with scientists from Columbia, John Hopkins and other universities.

Penning told that in the United States "it is decided at the level of each state if companies have an obligation to publicize the list of additives they use."

The industry established a voluntary database of used additives, on the fracking focus site. Penning explained that the additives used in the fracking fluid can be very varied and of many kinds, such as surfactants, corrosion inhibitors, biocides etc.

In toxicology they work on the basis that no chemical is safe, but that is the dose that makes the poison. Additives that could cause concern if they exceed safe levels are substitutes for benzene, ethylene glycol and formaldehyde.

"The potential toxicity of wastewater is difficult to assess because many chemical additives used in hydraulic fracturing fluid are undisclosed commercial secrets," Penning added.

The scientist also told that "the potential toxicity of wastewater is difficult to evaluate because it is a complex mixture (the additives can be antagonistic, synergistic or additive in their effects)".

Anthony Ingraffea, professor of engineering at Cornell University, warned of the impact of the September 2013 floods in Colorado, where only 20,000 wells are located in one county. "A good part of the infrastructure was destroyed, which means that the ponds with sewage tanks with chemical additives are now in the water courses and there are leakages of damaged gas pipelines." "The clear lesson is that infrastructure for fracking in floodplains should never be built.

What is done with wastewater?

These waters are what is known as flowback or reflux water, that is, injected water, with chemical additives and sand, which flows back when the gas starts to come out.

Approximately 25% to 75% of the injected fracturing fluid returns to the surface, according to the Royal Society. These wastewater is stored in open-pit tanks dug into the ground and covered (open pits), treated and reused or injected at high pressure into rock formations. The danger of leakage of wastewater is not unique to the extraction of shale gas, but is common in many industrial processes, notes the Royal Society.

“The wastewater may contain radioactive materials of natural occurrence, Naturally Ocurring Radioactive Materials, NORM, which are present in the shale rock in quantities significantly lower than the exposure limits," says the Royal Society report.

Can it exhaust water resources?

The use of water in large quantities in fracking operations is a cause of concern for some. "For natural gas, for example, fracking requires millions of gallons of water (around 2 to 5 million, or even more than 10 million, that is, from 7 to 18 or up to 37 million liters) for fracturing, which is several times more than conventional extraction requires, "John Rogers, senior energy analyst and co-manager of the Energy and Water Initiative of the Union of Concerned Scientists, Union of Scientists Aware, told.

"The extraction of shale gas by fracking consumes on average of 16 gallons of water per megawatt-hour, while conventional gas extraction uses 4. That is, fracking requires 4 times what conventional extraction requires, "said Rogers.

"That amount of water is less than what is involved in the extraction of coal, but the use of water is very localized and can be very important in the local scene, in terms of what would be available for other uses."

The Water-Smart Power study of the Union of Aware Scientists points out that about half of the hydraulic fracturing operations in the United States occur in regions with high or extremely high water stress, including Texas and Colorado.

Melissa Stark, global director of new energies at Accenture consultancy and author of the report "Shale gas water and exploitation", admits that the extraction of shale gas with hydraulic fracturing uses a lot of water (about 20 million liters per well), but notes that "it does not use more water than other industrial processes, such as irrigation for agriculture. The volumes required may seem large, but they are smaller compared to other water uses for agriculture, electric power generation and municipal use," he told.

Can there be methane leaks?
Anthony Ingraffea, professor of engineering at Cornell University in the United States, says that it is not about determining if wells can leak, but the question must be, what percentage has leaks?

Ingraffea analyzed the situation of the new 2012 wells in the Marcellus formation in Pennsylvania, based on the comments of the inspectors, according to records of the Pennsylvania Department of Environmental Protection.

According to Ingraffea, the inspectors registered 120 leaky wells, that is, they detected faults and leaks in 8.9% of the gas and oil exploration wells drilled in 2012.

A study published in September 2013 by the University of Texas, sponsored among others by nine oil companies, ensured that while methane leaks from shale gas extraction operations are substantial - more than one million tons per year - they were less than the estimates of the US Environmental Protection Agency.

However, the Association of Physicians, Scientists and Engineers for a Healthy Energy in the USA, of which Anthony Ingraffea is president, questioned the scientific rigor of that study, noting that the sample of 489 wells represents only 0.14% of wells in the country and also the wells analyzed were not selected at random "but in places and hours selected by the industry".

Some reported images of tap water that catches fire if a match is approached could be explained by the previous presence of methane.

"We must not forget that methane is a natural constituent of groundwater and in some places like Balcombe, where there were protests, the oil flows naturally to the surface," Richard Selley, professor emeritus of Imperial Petroleum Geology.

"We must remember that when a well is drilled and the aquifer area is crossed, three steel rings are placed, surrounded by cement, beneath the aquifer," added Selley.

How does global warming impact?

Between 1981 and 2005, US carbon emissions They increased 33%. But since 2005 they dropped by 9%. The reduction is due in part to the recession, but according to the US Energy Information Administration, Energy Information Administration, EIA, about half of that reduction is due to shale gas.

Globally, coal provides 40% of the world's electricity, according to the International Energy Agency, International Energy Agency. Advocates of shale gas extraction say it is cleaner than coal and can be a transition fuel, while expanding the use of renewable sources such as solar or wind energy.

In Spain, for example, renewable energies "are bordering 12% and there is an objective of the European Union so that by 2020 20% of European energies are renewable," said Luis Suarez, president of the Official College of Geologists of Spain, ICOG.

But others point out that the gas extracted in the process of hydraulic fracturing is methane, a gas much more potent than carbon dioxide as a greenhouse gas.

According to the Intergovernmental Panel on Climate Change, IPCC, a molecule of methane equals 72 of carbon dioxide after 20 years of emission, and 25 molecules of carbon dioxide at 100 years.

Robert Howarth and colleagues at Cornell University estimated that between 4 and 8% of the total methane production of a well escapes into the atmosphere and adds that there is also emission from the reflux waters that flow along with the gas to the atmosphere. surface after fracturing.

But this analysis is controversial. Lawrence Cathles, also of Cornell University, says the high potential for methane heating in 20 years must be counteracted by the fact that methane has a much shorter life in the atmosphere than CO2.

Robert Jackson of Duke University in North Carolina says that instead of worrying about fracking emissions themselves we should concentrate on leaks in the distribution chain. "Only in the city of Boston we found 3,000 methane leaks in the pipes," Jackson told to New Scientist magazine.

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